ramips: split base-files into subtargets

While most of the target's contents are split into subtargets, the
base-files are maintained for the target as a whole.

However, OpenWrt already implements a mechanism that will use (and
even prefer) files in the subtargets' directories. This can be
exploited to make several scripts subtarget-specific and thus save
some space.

In certain cases, keeping files in parent (=target) base-files was
more convenient, and thus no splitting was performed for those.

Note that this will increase overall code lines, but reduce code
per subtarget.

base-files ipk size reduction:
master (mt7621)   60958 B
split (mt7620)    46358 B (- 14.3 kiB)
split (mt7621)    48759 B (- 11.9 kiB)
split (mt76x8)    44948 B (- 15.6 kiB)
split (rt288x)    43508 B (- 17.0 kiB)
split (rt305x)    45616 B (- 15.0 kiB)
split (rt3883)    44176 B (- 16.4 kiB)

Run-tested on:
GL.iNet GL-MT300N-V2 (mt76x8)
D-Link DWR-116 (mt7620)

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/ramips/base-files/lib/preinit/04_handle_checksumming

@@ -1,56 +0,0 @@
-#!/bin/sh
-
-# Netgear WNCE2001 has does a checksum check on boot and goes into recovery
-# tftp mode when the check fails.  Initializing the JFFS2 partition triggers
-# this, so we make sure to zero checksum and size to be checksummed before
-# that happens, so this needs to run very early during boot.
-
-do_checksumming_disable() {
-	. /lib/functions.sh
-
-	local board=$(board_name)
-
-	case "$board" in
-	netgear,wnce2001)
-		echo "Board is WNCE2001, updating checksum partition..."
-		local zeroes=/dev/zero
-		local tmpfile=/tmp/wnce2001_checksum
-		local partname=checksum
-		local mtd=$(find_mtd_part $partname)
-		dd if=$mtd of=$tmpfile bs=80 count=1 2>/dev/null
-		signature=$(dd if=$tmpfile bs=1 skip=24 count=20 2>/dev/null)
-		checksum=$(dd if=$tmpfile bs=1 count=4 2>/dev/null | hexdump -v -n 4 -e '1/1 "%02x"')
-		if [ "$signature" != "RT3052-AP-WNCE2001-3" ]; then
-			echo "Signature of checksum partition is wrong, bailing."
-			return 0
-		fi
-		if [ "$checksum" != "00000000" ]; then
-			echo "Checksum is set, zeroing."
-			# zero out checksum
-			dd if=$zeroes of=$tmpfile conv=notrunc bs=1 seek=0 count=4 2>/dev/null
-			# zero out bytecount to be checksummed
-			dd if=$zeroes of=$tmpfile conv=notrunc bs=1 seek=60 count=4 2>/dev/null
-			mtd write $tmpfile $partname
-		else
-			echo "Checksum is already zero, nothing to do."
-		fi
-	;;
-	asus,rt-n56u)
-		echo "Board is ASUS RT-N56U, replacing uImage header..."
-		local firmware_mtd=$(find_mtd_part firmware)
-		local rootfs_mtd=$(find_mtd_part rootfs)
-		local rootfs_data_mtd=$(find_mtd_part rootfs_data)
-		local rootfs_len=$(grep \"rootfs\" /proc/mtd | awk -F' ' '{print "0x"$2}')
-		local rootfs_data_len=$(grep \"rootfs_data\" /proc/mtd | awk -F' ' '{print "0x"$2}')
-		local offset=$(echo "$rootfs_len $rootfs_data_len 0x40" | awk -F' ' '{printf "%i",$1-$2-$3}')
-		local signature=$(dd if=$rootfs_mtd skip=$offset bs=1 count=4 2>/dev/null | hexdump -v -n 4 -e '1/1 "%02x"')
-		if [ "$signature" = "27051956" ]; then
-			dd conv=notrunc if=$rootfs_mtd skip=$offset of=$firmware_mtd bs=1 count=64 2>/dev/null
-		fi
-	;;
-	esac
-
-	return 0
-}
-
-boot_hook_add preinit_main do_checksumming_disable