Fix interaction with new generic header stuff as added by:

	commit 6103ec56
	Author: Arnd Bergmann <arnd@arndb.de>
	Date:   Wed May 13 22:56:27 2009 +0000

	    asm-generic: add generic ABI headers

The problem is that asm/signal.h has been made to include asm-generic/signal.h,
but the redundant stuff from asm/signal.h has not been discarded, leading to
multiple redefinitions.

Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>