MAINTAINERS: add maintainers for DRM LOONGSON driver

This patch add Sui Jingfeng as maintainer to drm/loongson driver.
Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230615143613.1236245-3-15330273260@189.cn

MAINTAINERS

@@ -6959,6 +6959,13 @@ T:	git git://anongit.freedesktop.org/drm/drm-misc
 F:	drivers/gpu/drm/lima/
 F:	include/uapi/drm/lima_drm.h
 
+DRM DRIVERS FOR LOONGSON
+M:	Sui Jingfeng <suijingfeng@loongson.cn>
+L:	dri-devel@lists.freedesktop.org
+S:	Supported
+T:	git git://anongit.freedesktop.org/drm/drm-misc
+F:	drivers/gpu/drm/loongson/
+
 DRM DRIVERS FOR MEDIATEK
 M:	Chun-Kuang Hu <chunkuang.hu@kernel.org>
 M:	Philipp Zabel <p.zabel@pengutronix.de>