aaudio: clear data buffer before use

Just in case the HAL did not clear it.
This can prevent initial glitches on devices where the HAL
does not clear the buffer.

Bug: 186302619
Test: atest CtsNativeMediaAAudioTestCases
Change-Id: I2f437628adc81bcf8673494bc26d28a4dc5a03a0
1 file changed