mailmap: add entry for Gao Xiang

Add entry to connect all Gao Xiang's email addresses.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Acked-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

.mailmap

@@ -79,6 +79,8 @@ Frank Rowand <frowand.list@gmail.com> <frowand@mvista.com>
 Frank Rowand <frowand.list@gmail.com> <frank.rowand@am.sony.com>
 Frank Rowand <frowand.list@gmail.com> <frank.rowand@sonymobile.com>
 Frank Zago <fzago@systemfabricworks.com>
+Gao Xiang <xiang@kernel.org> <gaoxiang25@huawei.com>
+Gao Xiang <xiang@kernel.org> <hsiangkao@aol.com>
 Greg Kroah-Hartman <greg@echidna.(none)>
 Greg Kroah-Hartman <gregkh@suse.de>
 Greg Kroah-Hartman <greg@kroah.com>