ramips/mt7621: remove cflags override

Signed-off-by: Felix Fietkau <[email protected]>

target/linux/ramips/mt7621/target.mk

@@ -7,7 +7,6 @@ BOARDNAME:=MT7621 based boards
 FEATURES+=usb rtc
 CPU_TYPE:=1004kc
 CPU_SUBTYPE:=dsp
-CFLAGS:=-Os -pipe -mmt -mips32r2 -mtune=1004kc
 
 DEFAULT_PACKAGES += kmod-mt76