[PATCH] net/compat.h build fix

From: Andrew Morton <akpm@osdl.org>

Move the forward decl outside the ifdef, since we use it in both legs.

Should fix the spacr64 build error reported in
	http://bugzilla.kernel.org/show_bug.cgi?id=6625

Acked-by: "David S. Miller" <davem@davemloft.net>
Cc: Cedric Pellerin <cedric@bidouillesoft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>