aaudio: add histogram to clock model

Measure distribution of MMAP timestamp lateness.
This is used to discover the actual DSP timing behavior.
Turn histogram log on or off using a property.

Test: adb root
Test: adb shell setprop aaudio.log_mask 1
Test: run an AAudio MMAP program
Test: adb logcat | grep ClockModel
Change-Id: I910831d1feee43c59d1af2ac3135a910fef36fb2