aaudio: optimize float to int conversion

Use new techniques from audio_utils/primitives.h

Test: change volume while running
Test:     test_linear_ramp.cpp
Test:     adb shell write_sine_callback -pl -fi -x -s20
Test:     adb shell write_sine_callback -pl -ff -x -s20
Change-Id: Ib7dab07f351cf97a8cbda9608091188dec41d04c
1 file changed