audio: Adjust stream buffer size calculation

When calculating buffer size, use powers of two
for "large" buffers only on SRs >= 44100 Hz.
With lower SRs, sizes rounded up to a multiple
of 2 give too high latency.

Bug: 328432688
Test: repro steps from b/328432688#comment3
Test: atest VtsHalAudioCoreTargetTest
Change-Id: I605ef8507fef030d349e85c33ed0229c9566ddb5