wrappers for ->i_mutex access

parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested},
inode_foo(inode) being mutex_foo(&inode->i_mutex).

Please, use those for access to ->i_mutex; over the coming cycle
->i_mutex will become rwsem, with ->lookup() done with it held
only shared.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 87dc16d..166d3ed 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -262,7 +262,7 @@
 		.nr_to_write = 1,
 	};
 
-	WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));
+	WARN_ON_ONCE(!inode_is_locked(inode));
 	if (!iinfo->i_lenAlloc) {
 		if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_USE_SHORT_AD))
 			iinfo->i_alloc_type = ICBTAG_FLAG_AD_SHORT;