drm: msm: dsi-staging: add support to specify DSI PHY timings in panel dtsi

Some DSI panels require non-standard values of DSI PHY timings for
certain parameters for correct operation. The auto-calculated values
of DSI PHY timings in these cases can show some corruption issues on
the panel. Add support to pass DSI PHY timing parameters from the panel
dtsi in such cases. These value will supersede the PHY timing calculation
logic which is present in the DSI PHY driver.

CRs-Fixed: 2008002
Change-Id: I4a9f7b3352c488070e54f455b30bcc45851f1286
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>
Signed-off-by: Shashank Babu Chinta Venkata <sbchin@codeaurora.org>