drm/display/dsc: Add drm_dsc_get_bpp_int helper

Add helper to get the integer value of drm_dsc_config.bits_per_pixel

Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/539268/
Link: https://lore.kernel.org/r/20230329-rfc-msm-dsc-helper-v14-3-bafc7be95691@quicinc.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>