rp2/boards: Add SIL_RP2040_SHIM board by Silicognition LLC.

Add new board Silicognition RP2040-Shim, RP2040 with 4 MB of flash
and W5500 drivers included and configured by default for use with
the Silicognition PoE-FeatherWing.
Co-authored-by: Matt Trentini <matt.trentini@gmail.com>
Signed-off-by: Patrick Van Oosterwijck <patrick@silicognition.com>

ports/rp2/boards/SIL_RP2040_SHIM/board.json

+{
+    "deploy": [
+        "deploy.md"
+    ],
+    "docs": "",
+    "features": [
+        "Dual-core",
+        "RGB LED",
+        "External Flash",
+        "USB"
+    ],
+    "images": [
+        "rp2040-shim-product.jpg",
+        "RP2040-Shim-pinout.png"
+    ],
+    "mcu": "rp2040",
+    "product": "RP2040-Shim",
+    "thumbnail": "",
+    "url": "https://silicognition.com/Products/rp2040-shim/",
+    "vendor": "Silicognition LLC"
+}

ports/rp2/boards/SIL_RP2040_SHIM/deploy.md

+### Flashing via UF2 bootloader
+
+To get the board in bootloader mode ready for the firmware update, execute
+`machine.bootloader()` at the MicroPython REPL.  Alternatively, double press
+the reset button SW1.  The uf2 file below should then be copied to the USB mass
+storage device that appears.  Once programming of the new firmware is complete
+the device will automatically reset and be ready for use.

ports/rp2/boards/SIL_RP2040_SHIM/manifest.py

+include("$(PORT_DIR)/boards/manifest.py")
+
+require("bundle-networking")

ports/rp2/boards/SIL_RP2040_SHIM/mpconfigboard.cmake

+# cmake file for Silicognition RP2040-Shim
+set(PICO_BOARD none)
+set(MICROPY_PY_NETWORK_WIZNET5K W5500)
+set(MICROPY_PY_LWIP 1)
+set(MICROPY_FROZEN_MANIFEST ${MICROPY_BOARD_DIR}/manifest.py)

ports/rp2/boards/SIL_RP2040_SHIM/mpconfigboard.h

+// Board config for Silicognition RP2040-Shim
+
+#define MICROPY_HW_BOARD_NAME               "Silicognition RP2040-Shim"
+#define PICO_BOOT_STAGE2_CHOOSE_GENERIC_03H 1
+#ifndef PICO_FLASH_SIZE_BYTES
+#define PICO_FLASH_SIZE_BYTES               (4 * 1024 * 1024)
+#endif
+#define MICROPY_HW_FLASH_STORAGE_BYTES      (3 * 1024 * 1024)
+
+#define MICROPY_HW_USB_VID                  (0x1209)
+#define MICROPY_HW_USB_PID                  (0xF502)
+#undef  PICO_RP2040_B0_SUPPORTED
+#define PICO_RP2040_B0_SUPPORTED            0
+
+// Bus configuration
+#define MICROPY_HW_I2C0_SCL                 (17)
+#define MICROPY_HW_I2C0_SDA                 (16)
+
+#define MICROPY_HW_SPI0_SCK                 (18)
+#define MICROPY_HW_SPI0_MOSI                (19)
+#define MICROPY_HW_SPI0_MISO                (20)
+
+#define MICROPY_HW_SPI1_SCK                 (10)
+#define MICROPY_HW_SPI1_MOSI                (11)
+#define MICROPY_HW_SPI1_MISO                (12)
+
+// Enable networking
+#define MICROPY_PY_NETWORK                  (1)
+#define MICROPY_PY_NETWORK_HOSTNAME_DEFAULT "RP2040-Shim"
+
+// Wiznet HW config
+#define MICROPY_HW_WIZNET_SPI_ID            (1)
+#define MICROPY_HW_WIZNET_SPI_BAUDRATE      (20 * 1000 * 1000)
+#define MICROPY_HW_WIZNET_SPI_SCK           (10)
+#define MICROPY_HW_WIZNET_SPI_MOSI          (11)
+#define MICROPY_HW_WIZNET_SPI_MISO          (12)
+#define MICROPY_HW_WIZNET_PIN_CS            (21)
+// Since the PoE-FeatherWing doesn't connect RST, map RST by
+// default to an unused pin
+#define MICROPY_HW_WIZNET_PIN_RST           (9)
+
+// NeoPixel GPIO23, power not toggleable
+// Red user LED GPIO22

ports/rp2/boards/SIL_RP2040_SHIM/pins.csv

+A0,GPIO29
+A1,GPIO28
+A2,GPIO27
+A3,GPIO26
+D24,GPIO24
+D25,GPIO25
+SCK,GPIO10
+MOSI,GPIO11
+MISO,GPIO12
+D0,GPIO1
+D1,GPIO0
+D4,GPIO6
+SDA,GPIO16
+SCL,GPIO17
+D5,GPIO18
+D6,GPIO19
+D9,GPIO20
+D10,GPIO21
+D11,GPIO15
+D12,GPIO14
+D13,GPIO22
+LED,GPIO22
+NEOPIXEL,GPIO23