TouchpadInputMapper: protect metrics data with a lock

Since the data is pulled on a binder thread, there could be a
synchronization issue here.

Bug: 315939807
Test: atest 'android.input.cts.hostside.InputAtomsTest#testTouchpadUsageAtom_FingerAndPalmCounts'
Change-Id: I780c9e87ef28a11e383f819d7fd0ecaeac26c5d1
1 file changed