drm/msm/dsi-staging: remove unnecessary check for dynamic DSI clock

For dynamic DSI clock, remove unnecessary return status check, update
log output with more meaningful description and simplify related log
output to make code and log brief.

CRs-Fixed: 2212653
Change-Id: Ie2cfa565f3358217dbc407abfdf25563dfa55eec
Signed-off-by: Yujun Zhang <yujunzhang@codeaurora.org>