linux-phytec-ti

MAINTAINERS: update Xinming's email address

I'd like to use this new gmail from now on.

Cc: Ganapathi Bhat <gbhat@marvell.com>
Signed-off-by: Xinming Hu <huxm@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>