media: venus: vdec: Use pmruntime autosuspend

Implement pmruntime autosuspend in video decoder. This will
allow to save power while the userspace is inactive for some
reasonable period of time. Here we power-off venus core clocks
and power domain and don't touch vcodec because it is under
hardware control. The later decision is made to simplify the
code and avoid a mess in the power management code.

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>