scsi: lpfc: Make FW logging dynamically configurable

Currently, the FW logging facility is a load/boot time parameter which
requires the driver to be unloaded/reloaded or the system rebooted in order
to change its configuration.

Convert the logging facility to allow dynamic enablement and configuration.
Specifically:

 - Convert the feature so that it can be enabled dynamically via an
   attribute.  Additionally, the size of the buffer can be configured
   dynamically.

 - Add locks around states that now may be changing.

 - Tie the feature into debugfs so that the logs can be read at any time.

Link: https://lore.kernel.org/r/20191018211832.7917-12-jsmart2021@gmail.com
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>