powerpc/signal32: Fix sigset_t conversion when copying to user

On PPC64, put_sigset_t converts a sigset_t to a compat_sigset_t
before copying it to userspace. There is a typo in the case that
we have 4 words to copy, meaning that we corrupt the compat_sigset_t.

It appears that _NSIG_WORDS can't be greater than 2 at the moment
so this code is probably always optimised away anyway.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/signal_32.c

@@ -97,7 +97,7 @@ static inline int put_sigset_t(compat_sigset_t __user *uset, sigset_t *set)
 	compat_sigset_t	cset;
 
 	switch (_NSIG_WORDS) {
-	case 4: cset.sig[5] = set->sig[3] & 0xffffffffull;
+	case 4: cset.sig[6] = set->sig[3] & 0xffffffffull;
 		cset.sig[7] = set->sig[3] >> 32;
 	case 3: cset.sig[4] = set->sig[2] & 0xffffffffull;
 		cset.sig[5] = set->sig[2] >> 32;