MAINTAINERS: Update myself email address

Update myself email address.
Add John Stultz as a reviewer. Thanks John.
Update git tree to drm-misc

Signed-off-by: Xinliang Liu <xinliang.liu@linaro.org>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200220090328.25932-1-xinliang.liu@linaro.org