[SCSI] qla2xxx: Add input/output byte-count statistics.

Currently Firmware does not have counters for input megabytes and
output megabytes, therefore driver counts these values depending
on the status of the scsi command and direction of the command.
The values are exported in the FC_HOST path.

Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>