fscrypt: remove fscrypt_is_direct_key_policy()

fscrypt_is_direct_key_policy() is no longer used, so remove it.

Link: https://lore.kernel.org/r/20191209211829.239800-5-ebiggers@kernel.orgSigned-off-by: NEric Biggers <ebiggers@google.com>

fs/crypto/fscrypt_private.h

@@ -136,12 +136,6 @@ fscrypt_policy_flags(const union fscrypt_policy *policy)
 	BUG();
 }
 
-static inline bool
-fscrypt_is_direct_key_policy(const union fscrypt_policy *policy)
-{
-	return fscrypt_policy_flags(policy) & FSCRYPT_POLICY_FLAG_DIRECT_KEY;
-}
-
 /**
  * For encrypted symlinks, the ciphertext length is stored at the beginning
  * of the string in little-endian format.