usb_bam_data: Add flow control and protection

This change adds flow control and protection for
flow control variables. This is required when we
reach threshold for more number of packets which
we are queueing with IPA software, otherwise we
are going to end up consuming more memory by keep
allocating memory for received packets from host
machine which would results into OOM issue.

Change-Id: I09995aeca64ec96fae3cf07345721dcd847ea91f
Signed-off-by: Mayank Rana <mrana@codeaurora.org>