stm32/Makefile: Remove Wno-attributes for ll_usb HAL file.

This HAL file is now patched so it doesn't have these warnings.

ports/stm32/Makefile

@@ -319,7 +319,6 @@ SRC_HAL = $(addprefix $(HAL_DIR)/Src/stm32$(MCU_SERIES)xx_,\
 	)
 
 ifeq ($(MCU_SERIES),$(filter $(MCU_SERIES),f4 f7 h7 l4))
-$(BUILD)/$(HAL_DIR)/Src/stm32$(MCU_SERIES)xx_ll_usb.o: CFLAGS += -Wno-attributes
 SRC_HAL += $(addprefix $(HAL_DIR)/Src/stm32$(MCU_SERIES)xx_,\
 	hal_sd.c \
 	ll_sdmmc.c \