scsi: qedf: Correct xid range overlap between offloaded requests and libfc requests

There is currently an overlap where exchange IDs between what is used for
offloaded commands and by libfc for ELS commands.  Correct this so that
exchange ID range is:

Offloaded requests: 0 to 0xfff
libfc requests: 0x1000 to 0xfffe

Signed-off-by: Chad Dupuis <cdupuis@marvell.com>
Signed-off-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>