hwc/overlay: Fix decimation / bwc bugs

1) While setting BWC check for 90 transform and swap crop
2) Calculate decimation in the getDecimationFactor API itself.
   Currently, a residual downscale is calculated and the clients have
   to take logs and apply forcible decimation like in MdpCtrl
3) Fix bug where transform gets typecasted to bool

b/14225977

Change-Id: I3c99c571e02e2cf7822342516b6a87d97be553d1
5 files changed