usb_bam: Add support for dumping usbbam registers during panic

On some platforms, RMNET and RNDIS interfaces uses BAM2BAM
over IPA for data path. We might need USB BAM registers for
analyzing data stall issues, which results in target crash.
Hence add support for registering panic notifier callback
and also dumping USB BAM registers in callback when it is called
during panic.

Change-Id: I96c52e27307340c8ec5ae0f1f9e20cae0c7bd5bb
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>