drm/msm/dp: Reduce complexity in code

To increse readibilty, functions of larger length are refactored
based on different logic checks in the function. This change doesn't
change any functionality but only improves code readability.

Change-Id: Ib5262a6a6e1dc732f72be570c053aee1519cdaf0
Signed-off-by: Satya Rama Aditya Pinapala <psraditya30@codeaurora.org>