Fix ExternalVibrationUtils to be bound to [-1,1]

Fix scale functions to always return scaled values in [-1,1] range for
the haptics PCM channels.

Bug: 427912736
Flag: android.os.vibrator.vibration_scale_bounds_fix_enabled
Test: ExternalVibrationUtilsTest
Change-Id: I0811b7cba0cde1d6804c78bf5133baebc018a7bb