drm/ast: Add resolution support for 1152x864@75

Add 1152x864 into support list.

Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220916085058.3386-1-jammy_huang@aspeedtech.com