KEYS: Move the flags representing required permission to linux/key.h

Move the flags representing required permission to linux/key.h as the perm
parameter of security_key_permission() is in terms of them - and not the
permissions mask flags used in key->perm.

Whilst we're at it:

 (1) Rename them to be KEY_NEED_xxx rather than KEY_xxx to avoid collisions
     with symbols in uapi/linux/input.h.

 (2) Don't use key_perm_t for a mask of required permissions, but rather limit
     it to the permissions mask attached to the key and arguments related
     directly to that.

Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
diff --git a/security/capability.c b/security/capability.c
index 8b4f24a..c1426b9 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -878,7 +878,7 @@
 }
 
 static int cap_key_permission(key_ref_t key_ref, const struct cred *cred,
-			      key_perm_t perm)
+			      unsigned perm)
 {
 	return 0;
 }