msm: camera: csiphy: Clean up bringup seq for 3phase operation

There are some register duplicated to program bringup sequence for
3phase opertion based on datarate. This change removes duplicate
register settings, as well as renaming some macros for code
readability.

Change-Id: Idb1f617ca1bb749e9875647074781c91a385ec3c
Signed-off-by: Jigarkumar Zala <jzala@codeaurora.org>