We're trying to access vop registers here, so need to make sure
the pm domain is on.

Normally it should be enabled by the bootloader, but there's no
guarantee of it. And if we wanna do unbind/bind, it would also
cause the device to hang.

And this patch also does these:
1/ move vop_initial to the end of vop_bind for eaiser error handling.
2/ correct the err_put_pm_runtime of vop_enable.
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1491481885-13775-8-git-send-email-jeffy.chen@rock-chips.com