scsi: be2iscsi: Fix release of DHCP IP in static mode

If BOOTPROTO is changed to static, the DHCP IP address should be released.
All cases are being handled mgmt_set_ip and mgmt_static_ip_modify.

Rearrange IFACE APIs to:
beiscsi_if_clr_ip
beiscsi_if_set_ip
beiscsi_if_en_static
beiscsi_if_en_dhcp

This simplifies release of DHCP IP when BOOTPROTO is set to static.

Signed-off-by: Jitendra Bhivare <jitendra.bhivare@broadcom.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>