[SCSI] fnic: Remove QUEUE_FULL handling code

Remove fnic driver QUEUE_FULL handling code instead let SCSI mid layer
handle queue full and use its algorithm to ramp down/up queue

Signed-off-by: Suma Ramars <sramars@cisco.com>
Signed-off-by: Hiral Patel <hiralpat@cisco.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>