SF: fix a bug with DISPLAY_EVENT_MODE_CHANGE

SF might dispatch a DISPLAY_EVENT_MODE_CHANGE event before changing
the actual mode. This can happen when the mode change takes more than
a single refresh and caused by incorrectly checking the previously
reported event without checking for the current mode.

Bug: 194515308
Bug: 193945763
Test: SF unit tests
Change-Id: Icf44e0fb6aadb76e629cd408907389e2626d2047
Merged-In: Icf44e0fb6aadb76e629cd408907389e2626d2047