sdm: Cache command mode status during initialization

This function reduces time spent in HWCDisplay::IsDisplayCommandMode()
by caching the is_cmd_mode_ flag after querying fixed info once
during initialization and after dynamic mode switching through
SetDisplayMode().

CRs-Fixed: 2309620
Change-Id: Ib33f41030e8828f7a977893b33ba3819f4622286
3 files changed