xattr_handler: pass dentry and inode as separate arguments of ->get()

... and do not assume they are already attached to each other

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c
index 145d2b8..03224b0 100644
--- a/fs/btrfs/xattr.c
+++ b/fs/btrfs/xattr.c
@@ -369,11 +369,9 @@
 }
 
 static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
-				   struct dentry *dentry, const char *name,
-				   void *buffer, size_t size)
+				   struct dentry *unused, struct inode *inode,
+				   const char *name, void *buffer, size_t size)
 {
-	struct inode *inode = d_inode(dentry);
-
 	name = xattr_full_name(handler, name);
 	return __btrfs_getxattr(inode, name, buffer, size);
 }