qcom/audio/hal: add offset to MMAP input time

Try to fix glitches on AAudio MMAP input on some devices.
The DSP is returning a position/time pair that is too soon.

Set default offset to zero if no property used.
Remove unneeded FIXME.
Improve comments.
Cleanup adding of offset.

This CL combines two CLs from Q master. See Merged-in lines below.

Bug: 122680738
Test: Should see glitch.count = 0 when you run this test.
Test: adb shell aaudio_loopback -tm -s20

Change-Id: Ib4c5b773702923ef76da124a5c6f4773e004ed7e
Merged-In: Ib4c5b773702923ef76da124a5c6f4773e004ed7e
Merged-In: Idd85f8978443e036ba4c5fb6440320a8578a74fd
(cherry picked from commit 07b4288d)