powerpc/pkeys: Fix calculation of total pkeys.

Total number of pkeys calculation is off by 1. Fix it.

Fixes: 4fb158f65ac5 ("powerpc: track allocation status of all pkeys")
Cc: stable@vger.kernel.org # v4.16+
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/pkeys.c

@@ -92,7 +92,7 @@ int pkey_initialize(void)
 	 * arch-neutral code.
 	 */
 	pkeys_total = min_t(int, pkeys_total,
-			(ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT));
+			((ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT)+1));
 
 	if (!pkey_mmu_enabled() || radix_enabled() || !pkeys_total)
 		static_branch_enable(&pkey_disabled);