fix samd build

src/portable/microchip/samd21/dcd_samd21.c

@@ -127,7 +127,7 @@ void dcd_set_config (uint8_t rhport, uint8_t config_num)
 uint32_t dcd_get_microframe(uint8_t rhport)
 {
   (void) rhport;
-  return USB->DEVICE.FNUM & (TU_BIT(14) - 1);
+  return USB->DEVICE.FNUM.reg & (TU_BIT(14) - 1);
 }
 
 /*------------------------------------------------------------------*/

src/portable/microchip/samd51/dcd_samd51.c

@@ -132,7 +132,7 @@ void dcd_set_config (uint8_t rhport, uint8_t config_num)
 uint32_t dcd_get_microframe(uint8_t rhport)
 {
   (void) rhport;
-  return USB->DEVICE.FNUM & (TU_BIT(14) - 1);
+  return USB->DEVICE.FNUM.reg & (TU_BIT(14) - 1);
 }
 
 /*------------------------------------------------------------------*/