kernel/signal.c: use __ARCH_HAS_SA_RESTORER instead of SA_RESTORER

kernel/signal.c: use __ARCH_HAS_SA_RESTORER instead of SA_RESTORER

__ARCH_HAS_SA_RESTORER is the preferred conditional for use in 3.9 and
later kernels, per Kees.

Cc: Emese Revfy <[email protected]>
Cc: Emese Revfy <[email protected]>
Cc: PaX Team <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Serge Hallyn <[email protected]>
Cc: Julien Tinnes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>