usb: bam: make debug_event logging to more coherent

Current event logging supports only adding debug messages to buffer,
sometimes error messages also contains useful information. Adding
error messages along with debug message in buffer will give more
clear understanding.

This change adds support for adding error logs by introducing new
macro log_event_dbg() and log_event_err(). With these logs will be
available in kernel logs and log event buffer both. Also added
another macro log_event_none() with this logs will only be added to
log_event_buffer.

Also replace previous log_event() calls with log_event_debug() calls.

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

Change-Id: Ic5c0810fbe57399a77782b5a0edede8a985821e6
Signed-off-by: Tarun Gupta <tarung@codeaurora.org>