stm32/subghz: Add STM32WL55 subghz radio interface to stm module.

This is the minimum C interface to allow a modem driver to be built in
Python.  Interface is simple, with the intention that the micropython-lib
driver is the main (only) consumer of it.

Signed-off-by: Angus Gratton <angus@redyak.com.au>

ports/stm32/main.c

@@ -86,6 +86,7 @@
 #include "servo.h"
 #include "dac.h"
 #include "can.h"
+#include "subghz.h"
 
 #if MICROPY_PY_THREAD
 STATIC pyb_thread_t pyb_thread_main;
@@ -403,6 +404,9 @@ void stm32_main(uint32_t reset_mode) {
     #if defined(STM32WB)
     rfcore_init();
     #endif
+    #if defined(STM32WL)
+    subghz_init();
+    #endif
     #if MICROPY_HW_SDRAM_SIZE
     sdram_init();
     bool sdram_valid = true;
@@ -650,6 +654,9 @@ soft_reset_exit:
     #if MICROPY_PY_BLUETOOTH
     mp_bluetooth_deinit();
     #endif
+    #if defined(STM32WL)
+    subghz_deinit();
+    #endif
     #if MICROPY_PY_NETWORK
     mod_network_deinit();
     #endif