audio: Remove timeout from waits on event flags in HAL driver threads

This fixes a power regression caused by periodic wakeups of
the driver threads even when the device is idle.

The timeout is really not needed, it used to be there to ensure that
the thread exits its loop, but then an explicit wake-up call before
closing the thread had been added for this purpose.

Bug: 34682579
Test: Follow repro steps from the bug, compare power consumption
      to the legacy version of the audio HAL.

Change-Id: I0bfc2079a449894c5d0bd6ef19b53ca425795a9e