drm/amd/display: Set phy_mux_sel bit in dmub scratch register

drm/amd/display: Set phy_mux_sel bit in dmub scratch register

[Why]
B0 has pipe mux for DIGC and DIGD which can be connected to PHYF/PHYG or
PHYC/PHY D.

[How]
Based on chip internal hardware revision id determine it is B0 and set
DMUB scratch register so DMUBFW can connect the display pipe is
connected correctly to the dig.

Cc: Wayne Lin <wayne.lin@amd.com>
Cc: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Hansen <Hansen.Dsouza@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>