powerpc/mm/hash: Convert mask to unsigned long

This doesn't have any functional change. But helps in avoiding mistakes
in case the shift bit changes
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/book3s/64/mmu-hash.h

@@ -409,7 +409,7 @@ static inline unsigned long hpt_vpn(unsigned long ea,
 static inline unsigned long hpt_hash(unsigned long vpn,
 				     unsigned int shift, int ssize)
 {
-	int mask;
+	unsigned long mask;
 	unsigned long hash, vsid;
 
 	/* VPN_SHIFT can be atmost 12 */