[PATCH] m68k traps.c constraints

Cast is not an lvalue; =r constraint wants an lvalue and really couldn't
care whether it's void * or other pointer type.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>