scsi: be2iscsi: Add missing function parameter description

scsi: be2iscsi: Add missing function parameter description

Also promote fully documented function header to kerneldoc.

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

 drivers/scsi/be2iscsi/be_mgmt.c:112: warning: Function parameter or member 'phba' not described in 'mgmt_open_connection'

Link: https://lore.kernel.org/r/20200713080001.128044-20-lee.jones@linaro.org
Cc: Subbu Seetharaman <subbu.seetharaman@broadcom.com>
Cc: Ketan Mukadam <ketan.mukadam@broadcom.com>
Cc: Jitendra Bhivare <jitendra.bhivare@broadcom.com>
Cc: linux-drivers@broadcom.com
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>