AAudio: Scale capacity by device sample rate

We should scale capacity by the device sample rate instead of 48000.
Although 48000 works in most cases, some use cases don't use 48000 as
the default sample rate sample rate.

This involves adding this calculation in two separate places for the
exclusive and shared cases.

Bug: 382715299
Test: atest AAudioTests
Test: OboeTester Test Glitches
Flag: EXEMPT bugfix
Change-Id: Ie3b6bb69dd56abed029e39d377976baa7ddb49bc