floss: Align the read and write rate

The data length write to underlying device should be align with the data
read.

Also remove a log that no longer valid.

Tag: #floss
Bug: 213408429
Test: Build, flush and test with playback, capture
BYPASS_LONG_LINES_REASON: Bluetooth likes 120 char lines

Change-Id: Id7d6dd6e9d8aadd38b8bd4704b9646843a8b85d1