ext4: fix compile error when using BUFFER_TRACE

Fix compile error below when using BUFFER_TRACE.

fs/ext4/inode.c: In function ‘ext4_expand_extra_isize’:
fs/ext4/inode.c:5979:19: error: request for member ‘bh’ in something not a structure or union
  BUFFER_TRACE(iloc.bh, "get_write_access");

Fixes: c03b45b8 ("ext4, project: expand inode extra size if possible")
Signed-off-by: zhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>

fs/ext4/inode.c

@@ -5995,7 +5995,7 @@ int ext4_expand_extra_isize(struct inode *inode,
 
 	ext4_write_lock_xattr(inode, &no_expand);
 
-	BUFFER_TRACE(iloc.bh, "get_write_access");
+	BUFFER_TRACE(iloc->bh, "get_write_access");
 	error = ext4_journal_get_write_access(handle, iloc->bh);
 	if (error) {
 		brelse(iloc->bh);