selinux: Remove unnecessary check of array base in selinux_set_mapping()

'perms' will never be NULL since it isn't a plain pointer but an array
of u32 values.

This fixes the following warning when building with clang:

security/selinux/ss/services.c:158:16: error: address of array
'p_in->perms' will always evaluate to 'true'
[-Werror,-Wpointer-bool-conversion]
                while (p_in->perms && p_in->perms[k]) {
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/ss/services.c

@@ -157,7 +157,7 @@ static int selinux_set_mapping(struct policydb *pol,
 		}
 
 		k = 0;
-		while (p_in->perms && p_in->perms[k]) {
+		while (p_in->perms[k]) {
 			/* An empty permission string skips ahead */
 			if (!*p_in->perms[k]) {
 				k++;