libhwc2.1: OperationRateManager: save target operation rate

Save target operation rate instead of writing to the sysfs node
since we will change it via atomic commit path.

Bug: 284094183
Bug: 289042122
Test: change operation rate via brightness/config/power mode
Change-Id: I106de21ec0bb4094542aefc7b7109ab4dd9f304c
Merged-In: I106de21ec0bb4094542aefc7b7109ab4dd9f304c
2 files changed