net/ncsi: Add NCSI Broadcom OEM command

This patch adds OEM Broadcom commands and response handling. It also
defines OEM Get MAC Address handler to get and configure the device.

ncsi_oem_gma_handler_bcm: This handler send NCSI broadcom command for
getting mac address.
ncsi_rsp_handler_oem_bcm: This handles response received for all
broadcom OEM commands.
ncsi_rsp_handler_oem_bcm_gma: This handles get mac address response and
set it to device.

Signed-off-by: Vijay Khemka <vijaykhemka@fb.com>
Reviewed-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>