signal: Define __ARCH_HAS_SA_RESTORER so we know whether to clear sa_restorer

Vaguely based on upstream commit 574c4866e33d 'consolidate kernel-side
struct sigaction declarations'.

flush_signal_handlers() needs to know whether sigaction::sa_restorer
is defined, not whether SA_RESTORER is defined.  Define the
__ARCH_HAS_SA_RESTORER macro to indicate this.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/cris/include/asm/signal.h b/arch/cris/include/asm/signal.h
index ea6af9a..057fea2 100644
--- a/arch/cris/include/asm/signal.h
+++ b/arch/cris/include/asm/signal.h
@@ -122,6 +122,7 @@
 	void (*sa_restorer)(void);
 	sigset_t sa_mask;		/* mask last for extensibility */
 };
+#define __ARCH_HAS_SA_RESTORER
 
 struct k_sigaction {
 	struct sigaction sa;