ANDROID: sdcardfs: Fix locking for permission fix up

Iterating over d_subdirs requires taking d_lock.
Removed several unneeded locks.

Change-Id: I5b1588e54c7e6ee19b756d6705171c7f829e2650
Signed-off-by: Daniel Rosenberg <drosen@google.com>
diff --git a/fs/sdcardfs/lookup.c b/fs/sdcardfs/lookup.c
index a127d05..c74a7d1 100644
--- a/fs/sdcardfs/lookup.c
+++ b/fs/sdcardfs/lookup.c
@@ -387,11 +387,9 @@
 	if (dentry->d_inode) {
 		fsstack_copy_attr_times(dentry->d_inode,
 					sdcardfs_lower_inode(dentry->d_inode));
-		/* get drived permission */
-		mutex_lock(&dentry->d_inode->i_mutex);
+		/* get derived permission */
 		get_derived_permission(parent, dentry);
 		fix_derived_permission(dentry->d_inode);
-		mutex_unlock(&dentry->d_inode->i_mutex);
 	}
 	/* update parent directory's atime */
 	fsstack_copy_attr_atime(parent->d_inode,