MAINTAINERS: Add Sumit Semwal and Yongqin Liu as reviwers for kirin DRM driver

I no longer have access to the HiKey boards, so while I'm happy to
review code, I wanted to add Sumit and Yongqin to the reviewers list
so they would get CC'ed on future changes and would be able to have
a chance to validate and provide Tested-by: tags

Cc: Xinliang Liu <xinliang.liu@linaro.org>
Cc: Tian Tao  <tiantao6@hisilicon.com>
Cc: Yongqin Liu <yongqin.liu@linaro.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: kernel-team@android.com
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230120060956.1244187-1-jstultz@google.com