stm32/Makefile: Set CSUPEROPT to -Os for F0 and G0 MCUs to save space.

Saves 1804 bytes on NUCLEO_F091RC, and 1080 bytes on NUCLEO_G0B1RE.

Signed-off-by: Damien George <damien@micropython.org>

ports/stm32/Makefile

@@ -325,11 +325,8 @@ SRC_O += \
 	$(STARTUP_FILE) \
 	$(SYSTEM_FILE)
     
-ifeq ($(MCU_SERIES),l0)
-CSUPEROPT = -Os # save some code space
-endif
-
 ifeq ($(MCU_SERIES),$(filter $(MCU_SERIES),f0 g0 l0))
+CSUPEROPT = -Os # save some code space
 SRC_O += \
 	resethandler_m0.o \
 	shared/runtime/gchelper_m0.o