stm32g4: include desig support

Fixes: https://github.com/libopencm3/libopencm3/pull/1518
Reviewed-by: Karl Palsson <karlp@tweak.au>

lib/stm32/g4/Makefile

@@ -40,6 +40,7 @@ OBJS += cordic_common_v1.o
 OBJS += crs_common_all.o
 OBJS += crc_common_all.o crc_v2.o
 OBJS += dac_common_all.o dac_common_v2.o
+OBJS += desig_common_all.o desig_common_v1.o
 OBJS += dma_common_l1f013.o
 OBJS += dmamux.o
 OBJS += fdcan.o fdcan_common.o