scsi: csiostor: fix use after free in csio_hw_use_fwconfig()

mbp pointer is passed to csio_hw_validate_caps() so call mempool_free()
after calling csio_hw_validate_caps().

Signed-off-by: Varun Prakash <varun@chelsio.com>
Fixes: 541c571f

 ("csiostor:Use firmware version from cxgb4/t4fw_version.h")
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>