Don't pass any debug options directly to the assembler

When passing the -g option to gcc, gcc automatically selects a
suitable --g<format> option to pass on to the assembler.
Thus, there's no point in forcing a specific debug option on the
assembler using the -Wa mechanism.
Signed-off-by: NHaavard Skinnemoen <hskinnemoen@atmel.com>

config.mk

@@ -169,7 +169,9 @@ CFLAGS := $(CPPFLAGS) -Wall -Wno-trigraphs
 endif
 endif
 
-AFLAGS_DEBUG := -Wa,-g
+# $(CPPFLAGS) sets -g, which causes gcc to pass a suitable -g<format>
+# option to the assembler.
+AFLAGS_DEBUG :=
 
 # turn jbsr into jsr for m68k
 ifeq ($(ARCH),m68k)