aout: move STACK_TOP[_MAX] to asm/processor.h

Move STACK_TOP[_MAX] out of asm/a.out.h and into asm/processor.h as they're
required whether or not A.OUT format is available.

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>