m68knommu: use asflags instead of EXTRA_AFLAGS

Modify the extra asm flags for debugger capabilities, use asflags instead for
EXTRA_AFLAGS.  Suggestion from Sam Ravnborg.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>