switch xattr_handler->set() to passing dentry and inode separately

preparation for similar switch in ->setxattr() (see the next commit for
rationale).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/mm/shmem.c b/mm/shmem.c
index e418a99..a361449 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2645,10 +2645,11 @@
 }
 
 static int shmem_xattr_handler_set(const struct xattr_handler *handler,
-				   struct dentry *dentry, const char *name,
-				   const void *value, size_t size, int flags)
+				   struct dentry *unused, struct inode *inode,
+				   const char *name, const void *value,
+				   size_t size, int flags)
 {
-	struct shmem_inode_info *info = SHMEM_I(d_inode(dentry));
+	struct shmem_inode_info *info = SHMEM_I(inode);
 
 	name = xattr_full_name(handler, name);
 	return simple_xattr_set(&info->xattrs, name, value, size, flags);