ramips: remove set_preinit_iface script

This script isn't suitable for mt7621 anymore due to switching to DSA
and it needs a different preinit script.
Generic preinit logic in package/base-files has the ability to parse
board.json and pick preinit iface accordingly. Just remove this script
instead of moving it into subtargets.

Signed-off-by: Chuanhong Guo <gch981213@gmail.com>

target/linux/ramips/base-files/lib/preinit/07_set_preinit_iface_ramips

@@ -1,59 +0,0 @@
-#!/bin/sh
-#
-# Copyright (C) 2013 OpenWrt.org
-#
-
-. /lib/functions.sh
-
-ramips_switchdev_from_soc() {
-	# The ethernet switch driver enables VLAN by default, but
-	# failsafe uses eth0, making the device unreachable:
-	# https://dev.openwrt.org/ticket/18768
-
-	local switchdev
-	local RT3X5X=$(grep -E "(RT3.5|RT5350|MT7628|MT7688|MT7620|MT7621)" /proc/cpuinfo)
-
-	[ -n "$RT3X5X" ] || return 1
-
-	case "$RT3X5X" in
-	*MT7620*)
-		switchdev=mt7620
-		;;
-	*MT7621*)
-		switchdev=mt7530
-		;;
-	*)
-		switchdev=rt305x
-		;;
-	esac
-
-	echo "$switchdev"
-}
-
-ramips_switchdev_from_board() {
-	# For these devices, external ethernet switch should be used
-	# instead of the SoC internal switch.
-
-	local switchdev
-	local board=$(board_name)
-
-	case "$board" in
-	esac
-
-	echo "$switchdev"
-}
-
-ramips_set_preinit_iface() {
-	local switchdev=$(ramips_switchdev_from_board)
-	[ -n "$switchdev" ] || switchdev=$(ramips_switchdev_from_soc)
-
-	if [ -n "$switchdev" ]; then
-		swconfig dev $switchdev set reset 1
-		swconfig dev $switchdev set enable_vlan 0
-		swconfig dev $switchdev set apply 1
-	fi
-
-	ifname=eth0
-}
-
-boot_hook_add preinit_main ramips_set_preinit_iface