rockchip: video: Take the vop device out of standby

On reset the standby bit is clear, but if U-Boot is chain-loaded from
another boot loader it may be set. Clear it before starting up video so
that it works correctly.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Anatolij Gustschin <agust@denx.de>
Squashed in 'rockchip: video: fix taking the VOP device out of standby':
Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>