media: iris: don't specify max_channels in the source code

media: iris: don't specify max_channels in the source code

The UBWC max_channels spreading is specified in the Iris driver, but it
also can be calculated from the platform UBWC config. Use the platform
UBWC configuration instead of specifying it directly in the source.

Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Reviewed-by: Dikshita Agarwal <dikshita.agarwal@oss.qualcomm.com>
Tested-by: Wangao Wang <wangao.wang@oss.qualcomm.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Bryan O'Donoghue <bod@kernel.org>