MIPS: Fix GCC-4.6 'set but not used' warning in signal*.c

GCC-4.6 can find more unused code than previous versions could.

In the case of protected_restore_fp_context{,32}, the variable tmp is
really used.  Its use is tricky in that we really care about the side
effects of the __put_user() calls.  So we must mark tmp with
__maybe_unused to quiet the warning.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2035/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/signal.c

@@ -84,7 +84,7 @@ static int protected_save_fp_context(struct sigcontext __user *sc)
 
 static int protected_restore_fp_context(struct sigcontext __user *sc)
 {
-	int err, tmp;
+	int err, tmp __maybe_unused;
 	while (1) {
 		lock_fpu_owner();
 		own_fpu_inatomic(0);

arch/mips/kernel/signal32.c

@@ -115,7 +115,7 @@ static int protected_save_fp_context32(struct sigcontext32 __user *sc)
 
 static int protected_restore_fp_context32(struct sigcontext32 __user *sc)
 {
-	int err, tmp;
+	int err, tmp __maybe_unused;
 	while (1) {
 		lock_fpu_owner();
 		own_fpu_inatomic(0);