platform: msm_shared: cleanup DSI PHY programming for 28nm SoC

The DSI PHY register offset might be different for different chipsets.
Hence, cleanup the DSI PHY related code to make use of re-calculated
DSI PHY register base offsets instead of the DSI register base macros
present in iomap header files.

Change-Id: Ib8d32385f4a3a0ca1f04cb9f187e17cd4b4b443f
1 file changed