MAINTAINERS: Add a maintainer for the HiSilicon v3xx SFC driver

Set John Garry @ Huawei as the maintainer.

Signed-off-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/1575900490-74467-4-git-send-email-john.garry@huawei.com


Signed-off-by: Mark Brown <broonie@kernel.org>