brcm63xx: make wifi_bringup common for all boards

conditions for non-wifi boards to be handled later

iopsys-brcm63xx-arm/smarthub3/base-files/etc/init.d/wifi_bringup

-#!/bin/sh /etc/rc.common
-#
-# Load broadcom wifi drivers
-
-
-START=18
-
-boot() {
-	BOARDID=$(cat /proc/nvram/boardid)
-	NVM_FILE="${BOARDID}.nvm"
-
-	[ ! -s /etc/wlan/kernel_nvram.setting -a -s /etc/wlan/kernel_nvram.fallback ] && \
-		cp  /etc/wlan/kernel_nvram.fallback /etc/wlan/kernel_nvram.setting
-
-	[ -f "/data/$NVM_FILE" ] && \
-		ln -sf "/data/$NVM_FILE" "/etc/wlan/nvram/$NVM_FILE"
-
-	/etc/init.d/hndnvram.sh start && \
-		[ -s /data/.kernel_nvram.setting ] && \
-		/etc/init.d/bcm-wlan-drivers.sh start || \
-		echo "Failed to bring up wifi - fix and load wifi drivers manually"
-}