drm/msm: display changes for 6.12

DPU:

• Fix implement DP/PHY mapping on SC8180X
• Enable writeback on SM8150, SC8180X, SM6125, SM6350

DP:

• Enable widebus on all relevant chipsets

DSI:

• Fix PHY programming on SM8350 / SM8450

HDMI:

• Add support for HDMI on MSM8998

MDP5:

• NULL string fix