Fix issue 197683: English IME key-press latency is noticeably higher on...

Fix issue 197683: English IME key-press latency is noticeably higher on passion than sholes. Part 2.

Reduce sleep time in AudioFlinger mixer thread when no data has been written to output to speed up startup time when  exiting standby.

The rest of the modifications for this issues is in kernel driver:
 commit 0dbb0ee136ed8de757df1ae26d84556c1751deae for buffer size modification from 8192 to 4800 bytes.
Another kernel improvement that is not submitted yes will reduce delay when audio output is exiting standby.