scsi: cxgb3i: Remove bad documentation and demote kerneldoc header

scsi: cxgb3i: Remove bad documentation and demote kerneldoc header

Also move the header block above the correct function.

Fixes the following W=1 kernel build warning(s):

 drivers/scsi/cxgbi/cxgb3i/cxgb3i.c:390: warning: Function parameter or member 'dev' not described in 'arp_failure_skb_discard'
 drivers/scsi/cxgbi/cxgb3i/cxgb3i.c:390: warning: Function parameter or member 'skb' not described in 'arp_failure_skb_discard'
 drivers/scsi/cxgbi/cxgb3i/cxgb3i.c:390: warning: Excess function parameter 'c3cn' description in 'arp_failure_skb_discard'
 drivers/scsi/cxgbi/cxgb3i/cxgb3i.c:390: warning: Excess function parameter 'req_completion' description in 'arp_failure_skb_discard'
 drivers/scsi/cxgbi/cxgb3i/cxgb3i.c:895: warning: Function parameter or member 'csk' not described in 'l2t_put'
 drivers/scsi/cxgbi/cxgb3i/cxgb3i.c:895: warning: Excess function parameter 'c3cn' description in 'l2t_put'

Link: https://lore.kernel.org/r/20200721164148.2617584-41-lee.jones@linaro.org
Cc: Karen Xie <kxie@chelsio.com>
Cc: Dimitris Michailidis <dm@chelsio.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>