media: venus: pm: Hook 6xx pm ops into 4xx pm ops

At this time there is no need to differentiate between the two, we can
reuse the 4xx pm ops callback structure for 6xx.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>