mailbox: cmdq: support mt6779 gce platform definition

Add gce v4 hardware support with different thread number and shift.

Signed-off-by: Dennis YC Hsieh <dennis-yc.hsieh@mediatek.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: Bibby Hsieh <bibby.hsieh@mediatek.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>