Added support to retrieve driver version from a new sysfs variable called
driver_version. It makes it easier for the user to figure out the driver
version that is currently running.
Signed-off-by: Raghava Aditya Renukunta <RaghavaAditya.Renukunta@microsemi.com> Reviewed-by: David Carroll <David.Carroll@microsemi.com> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>