disp: msm: dp: fix the dsc line buf bit depth selection for dp dsc

The line buffer bit depth is used as part of dp
dsc calculations. Read the max supported line buf
bit depth supported by sink, and use that
restriction as part of the dsc calculations.

CRs-Fixed: 2325207
Change-Id: I4c995acad5f484edd1b438bdbf6c145b2d35ee41
Signed-off-by: Fuad Hossain <fhossain@codeaurora.org>