usb: bam: Add debug_event logging to usb_bam driver

Add event logging in usb_bam driver which logs events in a buffer
which can be retrieved in crash situation to help in debugging
issues. With log_event(dlog, x...) If we pass first argument as 1,
we maintain compatibility with dynamic debug and get logs in kernel
logs if dynamic debug is enabled.

To disable event_logging in buffer
echo 0 > /sys/module/usb_bam/parameters/enable_event_log

Change-Id: Ic278e504ce7cd551579c7994fa51a3b97cc42c76
Signed-off-by: Tarun Gupta <tarung@codeaurora.org>
Signed-off-by: Azhar Shaikh <azhars@codeaurora.org>