stm32/boards/NUCLEO_WB55: Enable MBOOT with packing mode.

To have at least one board configured with MBOOT_ENABLE_PACKING, for CI
testing purposes and demonstration of the feature.
Signed-off-by: Damien George <damien@micropython.org>

ports/stm32/boards/NUCLEO_WB55/mboot_keys.h

+//const uint8_t mboot_pack_sign_secret_key[] = {0xf1,0xd8,0x66,0x08,0xbc,0x78,0x39,0x65,0x6a,0xf4,0x88,0xf4,0x43,0x4d,0x10,0xfe,0x4f,0x79,0xb9,0xc3,0x77,0x36,0x23,0xc8,0xcf,0x62,0xa1,0x90,0xf1,0xdc,0xd9,0xbc,0xb2,0x2e,0x59,0x1e,0x53,0x04,0x54,0xd5,0xd1,0x3a,0x6d,0x2e,0x79,0x3e,0xb5,0x70,0xb4,0x9f,0x33,0xff,0x90,0x1d,0xc3,0x54,0x90,0x12,0x96,0x79,0xf4,0xed,0x56,0x75};
+const uint8_t mboot_pack_sign_public_key[] = {0xb2,0x2e,0x59,0x1e,0x53,0x04,0x54,0xd5,0xd1,0x3a,0x6d,0x2e,0x79,0x3e,0xb5,0x70,0xb4,0x9f,0x33,0xff,0x90,0x1d,0xc3,0x54,0x90,0x12,0x96,0x79,0xf4,0xed,0x56,0x75};
+const uint8_t mboot_pack_secretbox_key[] = {0x4a,0xbe,0x9b,0xed,0x55,0x9f,0x74,0xeb,0x1e,0x70,0xde,0xf5,0x19,0x0a,0xeb,0xa5,0x68,0xea,0xb0,0x88,0xe6,0xfe,0x4d,0x10,0x69,0x23,0x06,0x7f,0xdd,0x83,0xf0,0xbf};
+
+// The above keys are for demonstration purposes only, do not use them in production!

ports/stm32/boards/NUCLEO_WB55/mpconfigboard.mk

+# By default this board is configured to use mboot with packing (signing and encryption)
+# enabled.  Mboot must be deployed first.
+USE_MBOOT ?= 1
+
 MCU_SERIES = wb
 CMSIS_MCU = STM32WB55xx
 AF_FILE = boards/stm32wb55_af.csv
@@ -17,3 +21,6 @@ endif
 MICROPY_PY_BLUETOOTH = 1
 MICROPY_BLUETOOTH_NIMBLE = 1
 MICROPY_VFS_LFS2 = 1
+
+# Mboot settings
+MBOOT_ENABLE_PACKING = 1