MAINTAINERS: Update GPU driver maintainer information

I and Qianhai are GPU R&D engineers at Loongson, specializing
in kernel driver development. We understand that the current
Loongson GPU driver lacks dedicated maintenance resources
because of some reasons.

As Loongson GPU driver developers, we have both the capability
and the responsibility to continuously maintain the Loongson
GPU driver, ensuring minimal impact on its users. After internal
discussions, our team has decided to recommend me and Qianhai
to take over the maintenance responsibilities, and recommend
Huacai, Mingcong and Ruoyao to help to review.

And We'll continue to maintain it for current supported chips
and drive future updates according to chip support plan.

Signed-off-by: Jianmin Lv <lvjianmin@loongson.cn>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patch.msgid.link/20260320101012.22714-1-lvjianmin@loongson.cn