ARM: bcm283x: Switch V3D over to using the PM driver instead of firmware.

The GRAFX domain only contains V3D, and this driver should be the only
accessor of V3D (firmware usage gets disabled when V3D is in the DT),
so we can safely make Linux control the GRAFX and GRAFX_V3D power
domains.

Signed-off-by: Eric Anholt <eric@anholt.net>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>