msm: sde: Fix SW timestamp initialization when missing power event

Under some cases, the PM event is missing, and rotator driver will not
initialize the SW timestamp. This change is to add rotator reset
detection logic and auto initialize the SW timestamp register if such
happened.

CRs-Fixed: 2006856
Change-Id: I8c889435e0be1518a6ec2dd6f9c7b02d140df9f1
Signed-off-by: Benjamin Chan <bkchan@codeaurora.org>