USB: u_bam: Avoid workqueue for data received from BAM DMUX layer

BAM DMUX driver gives the data to the USB in work context and USB
is once again scheduling work for sending the data to the host.
This change avoid's the double work queue scheduling for the data
received from BAM DMUX, which might reduce the cpu usage and improve
the throughputs.

Change-Id: Ib66bc7f46f9436704e0d28b72771de50462ddf4b
Signed-off-by: Chiranjeevi Velempati <cvelempa@codeaurora.org>