mailmap: add Changbin Du

Add my email in the mailmap file to have a consistent shortlog output.

Link: http://lkml.kernel.org/r/20190308142103.4929-1-changbin.du@gmail.comSigned-off-by: NChangbin Du <changbin.du@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

.mailmap

@@ -224,3 +224,5 @@ Yakir Yang <kuankuan.y@gmail.com> <ykk@rock-chips.com>
 Yusuke Goda <goda.yusuke@renesas.com>
 Gustavo Padovan <gustavo@las.ic.unicamp.br>
 Gustavo Padovan <padovan@profusion.mobi>
+Changbin Du <changbin.du@intel.com> <changbin.du@intel.com>
+Changbin Du <changbin.du@intel.com> <changbin.du@gmail.com>