Limit AudioFlinger log.

AudioFlinger logs a warning when a write to the audio HAL
takes too long to return. The threshold for this warning is
a rule of thumb based on the assumption that the audio HAL will consume
buffers at a regular pace.
The introduction of low power audio mode with larger buffers and writes
occuring in bursts makes that this threshold is often exceeded resulting
in excessive and misleading warnings.

The threshold is raised to remove unwanted warnings but we should reconsider
the usefulness of this warning altogether.

Change-Id: I5ef6898ea28d879cede3e47da542a64092a3cca4