soc: mediatek: cmdq: add read_s function

Add read_s function in cmdq helper functions which support read value from
register or dma physical address into gce internal register.

Signed-off-by: Dennis YC Hsieh <dennis-yc.hsieh@mediatek.com>
Link: https://lore.kernel.org/r/1594136714-11650-5-git-send-email-dennis-yc.hsieh@mediatek.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>