scsi: lpfc: add support to retrieve firmware logs

This patch adds the ability to read firmware logs from the adapter. The driver
registers a buffer with the adapter that is then written to by the adapter.
The adapter posts CQEs to indicate content updates in the buffer. While the
adapter is writing to the buffer in a circular fashion, an application will
poll the driver to read the next amount of log data from the buffer.

Driver log buffer size is configurable via the ras_fwlog_buffsize sysfs
attribute. Verbosity to be used by firmware when logging to host memory is
controlled through the ras_fwlog_level attribute.  The ras_fwlog_func
attribute enables or disables loggy by firmware.

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>