drm: msm: dsi-staging: add support for DSI PHY v3.0

Add support for DSI PHY h/w driver for DSI PHY v3.0 which
is present on msm8998. This includes reorganising the DSI
PHY timing calculation logic which is common between DSI
PHY v2.0 and v3.0.

CRs-Fixed: 2008002
Change-Id: I789cf1d618a0dd27935f38438af7dde35810e80f
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>
Signed-off-by: Shashank Babu Chinta Venkata <sbchin@codeaurora.org>