firmware: meson_sm: Add secure power domain support

The Amlogic Meson A1/C1 Secure Monitor implements calls to control power
domain.

Signed-off-by: Jianxin Pan <jianxin.pan@amlogic.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Link: https://lore.kernel.org/r/1579087831-94965-2-git-send-email-jianxin.pan@amlogic.com