remoteproc/mediatek: add SCP support for mt8183

Provide a basic driver to control Cortex M4 co-processor

Signed-off-by: Erin Lo <erin.lo@mediatek.com>
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Signed-off-by: Pi-Hsun Shih <pihsun@chromium.org>
Link: https://lore.kernel.org/r/20191112110330.179649-3-pihsun@chromium.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>