media: venus: fix calculating mbps in calculate_inst_freq()

Currently in calculate_inst_freq(), video driver is calculating
macro blocks per frame instead of macro blocks per second(mpbs).
Which results frequency is always setting to lower frequency (150MHz)
as per frequency table for sc7180. Hence the playback is not smooth.

Corrected this by correcting the mbps calculation in calculate_inst_freq().

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