bluetooth: correct rfcomm command and reply formatting

The format of COMMAND line sent from HS to AG is COMMAND<cr>
The format of RESPONSE line sent from AG to HS is <cr><lf>RESPONSE<cr><lf>

Split rfcomm_write into rfcomm_write_command and rfcomm_write_response to handle
line formatting correctly.

Part-of: <pulseaudio/pulseaudio!520>
3 jobs for pr/fix-rfcomm-write-command-line-format-in-master in 5 minutes and 2 seconds (queued for 1 second)