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/efivarfs/file.c b/fs/efivarfs/file.c
index 90001da..c424e48 100644
--- a/fs/efivarfs/file.c
+++ b/fs/efivarfs/file.c
@@ -50,9 +50,9 @@
 		d_delete(file->f_path.dentry);
 		dput(file->f_path.dentry);
 	} else {
-		mutex_lock(&inode->i_mutex);
+		inode_lock(inode);
 		i_size_write(inode, datasize + sizeof(attributes));
-		mutex_unlock(&inode->i_mutex);
+		inode_unlock(inode);
 	}
 
 	bytes = count;