scsi: be2iscsi: Fix misdocumentation of 'pcontext'

Also demote unintentional kerneldoc header.

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

 drivers/scsi/be2iscsi/be_main.c:986: warning: Function parameter or member 'pcontext' not described in 'alloc_wrb_handle'
 drivers/scsi/be2iscsi/be_main.c:986: warning: Excess function parameter 'pwrb_context' description in 'alloc_wrb_handle'
 drivers/scsi/be2iscsi/be_main.c:1409: warning: Function parameter or member 'beiscsi_conn' not described in 'beiscsi_complete_pdu'
 drivers/scsi/be2iscsi/be_main.c:1409: warning: Function parameter or member 'phdr' not described in 'beiscsi_complete_pdu'
 drivers/scsi/be2iscsi/be_main.c:1409: warning: Function parameter or member 'pdata' not described in 'beiscsi_complete_pdu'
 drivers/scsi/be2iscsi/be_main.c:1409: warning: Function parameter or member 'dlen' not described in 'beiscsi_complete_pdu'

Link: https://lore.kernel.org/r/20200713080001.128044-19-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>