disp: msm: sde: fix input_handler operations for various usecases

Input event handler can be unregistered without being
registered in the case where DMS or DYN_CLK flags
are enabled on first commit, add changes to handle
this sequence.

Change-Id: Idf4f9f310b5d56df396bfa5c6477e94d4fae7a9f
Signed-off-by: Jayaprakash <jmadiset@codeaurora.org>