soc: amlogic: meson-gx-pwrc-vpu: fix power-off when powered by bootloader

In the case the VPU power domain has been powered on by the bootloader
and no driver are attached to this power domain, the genpd will power it
off after a certain amount of time, but the clocks hasn't been enabled
by the kernel itself and the power-off will trigger some faults.
This patch enable the clocks to have a coherent state for an eventual
poweroff and switches to the pm_domain_always_on_gov governor.

Fixes: 75fcb5ca

 ("soc: amlogic: add Meson GX VPU Domains driver")
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Tested-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>