libhwc2.1: remove unnecessary property_get

First, we remove property_get for checking the camera preview.
This is probably a legacy code which we don't use anymore.

Second, we remove unnecessary call to ExynosCompositionInfo's
constructor which contains a property_get.

Test: simpleperf profiler
Bug: 205901755
Change-Id: I1f7aba3cdfbbb7f75f3dd39c9ed06dc5366f07ac
3 files changed