usb_bam_data: Cleanup USB requests and allocated data buffers

On USB Cable disconnect, it is required to free USB requests and related
USB data buffers (SKBs). This change takes freeing USB requests (both
IN and OUT) and used data buffers with it. This fixes memory leak issues
on USB cable PO/PI case.

Also add few counters for track number of SKBs and requests being used
in SYS2BAM path.

CRs-Fixed: 703606
Change-Id: Id1b22de1b776209d48c66a9625fda2c2768ad7f0
Signed-off-by: Mayank Rana <mrana@codeaurora.org>