drm/mediatek: support maximum 64 mutex mod

This patch support that if modules more than 32,
add index more than 31 when using DISP_REG_MUTEX_MOD2 bit

Signed-off-by: Stu Hsieh <stu.hsieh@mediatek.com>
Signed-off-by: CK Hu <ck.hu@mediatek.com>