fscrypt: switch from ->is_encrypted() to IS_ENCRYPTED()

IS_ENCRYPTED() now gives the same information as
i_sb->s_cop->is_encrypted() but is more efficient, since IS_ENCRYPTED()
is just a simple flag check.  Prepare to remove ->is_encrypted() by
switching all callers to IS_ENCRYPTED().

Acked-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c
index 018c588..236a68d 100644
--- a/fs/crypto/keyinfo.c
+++ b/fs/crypto/keyinfo.c
@@ -268,7 +268,7 @@ int fscrypt_get_encryption_info(struct inode *inode)
 	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
 	if (res < 0) {
 		if (!fscrypt_dummy_context_enabled(inode) ||
-		    inode->i_sb->s_cop->is_encrypted(inode))
+		    IS_ENCRYPTED(inode))
 			return res;
 		/* Fake up a context for an unencrypted directory */
 		memset(&ctx, 0, sizeof(ctx));