Staging: Fixed a Cflag

Signed-off-by: Cyber Knight <cyberknight755@gmail.com>

Author: cyberknight777

drivers/staging/rtl8812au/Makefile

@@ -5,7 +5,7 @@ EXTRA_CFLAGS += -Wno-unused-variable
 EXTRA_CFLAGS += -Wno-unused-label
 #EXTRA_CFLAGS += -Wno-unused-parameter
 EXTRA_CFLAGS += -Wno-unused-function
-EXTRA_CFLAGS += -Wimplicit-fallthrough=0
+EXTRA_CFLAGS += -Wimplicit-fallthrough
 #EXTRA_CFLAGS += -Wno-parentheses-equality
 #EXTRA_CFLAGS += -Wno-pointer-bool-conversion
 EXTRA_CFLAGS += -Wno-unknown-pragmas