Switch SAMD51 and SAME51 back to -Os from -O2

The SAMx51 builds were getting very close to full on larger translations. This PR
adds 1400 bytes of enabled features, and pushed some over the edge.

Author: dhalbert

ports/atmel-samd/Makefile

@@ -94,14 +94,14 @@ endif
 
 ifeq ($(CHIP_FAMILY), samd51)
 PERIPHERALS_CHIP_FAMILY=sam_d5x_e5x
-OPTIMIZATION_FLAGS ?= -O2 -fno-inline-functions
+OPTIMIZATION_FLAGS ?= -Os
 # TinyUSB defines
 CFLAGS += -DCFG_TUSB_MCU=OPT_MCU_SAMD51 -DCFG_TUD_MIDI_RX_BUFSIZE=128 -DCFG_TUD_CDC_RX_BUFSIZE=256 -DCFG_TUD_MIDI_TX_BUFSIZE=128 -DCFG_TUD_CDC_TX_BUFSIZE=256 -DCFG_TUD_MSC_BUFSIZE=1024
 endif
 
 ifeq ($(CHIP_FAMILY), same51)
 PERIPHERALS_CHIP_FAMILY=sam_d5x_e5x
-OPTIMIZATION_FLAGS ?= -O2 -fno-inline-functions
+OPTIMIZATION_FLAGS ?= -Os
 # TinyUSB defines
 CFLAGS += -DCFG_TUSB_MCU=OPT_MCU_SAME5X -DCFG_TUD_MIDI_RX_BUFSIZE=128 -DCFG_TUD_CDC_RX_BUFSIZE=256 -DCFG_TUD_MIDI_TX_BUFSIZE=128 -DCFG_TUD_CDC_TX_BUFSIZE=256 -DCFG_TUD_MSC_BUFSIZE=1024
 endif