rp2: Change to use TinyUSB dcd_event_handler hook.

This change:
- Has a small code size reduction.
- Should slightly improve overall performance.  The old hook code
  seemed to use between 0.1% and 1.6% of the total CPU time doing no-op
  calls even when no USB work was required.
- USB performance is mostly the same, there is a small increase in
  latency for some workloads that seems to because sometimes the hook
  usbd_task() is called at the right time to line up with the next USB host
  request.  This only happened semi-randomly due to the timing of the hook.
  Improving the wakeup latency by switching rp2 to tickless WFE allows the
  usbd_task() to run in time for the next USB host request almost always,
  improving performance and more than offsetting this impact.

This work was funded through GitHub Sponsors.
Signed-off-by: Angus Gratton <angus@redyak.com.au>

ports/rp2/CMakeLists.txt

@@ -406,6 +406,7 @@ target_compile_options(${MICROPY_TARGET} PRIVATE
 
 target_link_options(${MICROPY_TARGET} PRIVATE
     -Wl,--defsym=__micropy_c_heap_size__=${MICROPY_C_HEAP_SIZE}
+    -Wl,--wrap=dcd_event_handler
 )
 
 set_source_files_properties(

ports/rp2/mpconfigport.h

@@ -250,23 +250,8 @@ extern void mp_thread_end_atomic_section(uint32_t);
 #define MICROPY_PY_LWIP_REENTER lwip_lock_acquire();
 #define MICROPY_PY_LWIP_EXIT    lwip_lock_release();
 
-#if MICROPY_HW_ENABLE_USBDEV
-#define MICROPY_HW_USBDEV_TASK_HOOK extern void usbd_task(void); usbd_task();
-#define MICROPY_VM_HOOK_COUNT (10)
-#define MICROPY_VM_HOOK_INIT static uint vm_hook_divisor = MICROPY_VM_HOOK_COUNT;
-#define MICROPY_VM_HOOK_POLL if (get_core_num() == 0 && --vm_hook_divisor == 0) { \
-        vm_hook_divisor = MICROPY_VM_HOOK_COUNT; \
-        MICROPY_HW_USBDEV_TASK_HOOK \
-}
-#define MICROPY_VM_HOOK_LOOP MICROPY_VM_HOOK_POLL
-#define MICROPY_VM_HOOK_RETURN MICROPY_VM_HOOK_POLL
-#else
-#define MICROPY_HW_USBDEV_TASK_HOOK
-#endif
-
 #define MICROPY_EVENT_POLL_HOOK_FAST \
     do { \
-        if (get_core_num() == 0) { MICROPY_HW_USBDEV_TASK_HOOK } \
         extern void mp_handle_pending(bool); \
         mp_handle_pending(true); \
     } while (0)