soc: amlogic: pm-domains: use always-on flag

Rather than use a governor to keep these domains always-on, instead
use the flag GENPD_FLAG_ALWAYS_ON.  This has the same effect, but with
much lower overhead since the governor path is not used at all.

Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Link: https://lore.kernel.org/r/20200921222135.7145-1-khilman@baylibre.com