media: venus: helpers: keep max bandwidth when mbps exceeds the supported range

When the video usecase have macro blocks per sec which is  more than
supported, keep the required bus bandwidth as the maximum supported.

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