media: venus: pm: Toggle 6xx wrapper power in vcodec_control

When in vcodec_control_v4() on the 4xx path we select between one of two
vcodec cores to toggle power control bits. In 6xx there is only one core
which offsets the relevant control registers to a slightly different
address.

This patch accounts for the address offset for 6xx silicon.

Co-developed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Dikshita Agarwal <dikshita@codeaurora.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>