ar71xx: add AVM FRITZ!WLAN Repeater 300E support

Specifications:
* SoC: AR7242 (Virian 400MHz)
* RAM: 64 MB DDR (W9751G6JB-25)
* Flash: 16MB SPI flash (S25FL129PIF)
* WiFi: AR9382 (2.4/5GHz) + 2x SE2595L
* LAN: 1x1000M (PEF7071V)

To install LEDE via EVA bootloader, a FTP connection need to be
established to 192.168.178.1 within the first seconds after power on:

  ftp> quote USER adam2
  ftp> quote PASS adam2
  ftp> binary
  ftp> debug
  ftp> passive
  ftp> quote MEDIA FLSH
  ftp> put lede-ar71xx-generic-fritz300e-squashfs-sysupgrade.bin mtd1

Signed-off-by: Mathias Kresin <dev@kresin.me>

target/linux/ar71xx/base-files/etc/hotplug.d/firmware/10-ath9k-eeprom

@@ -40,6 +40,24 @@ ath9k_ubi_eeprom_extract() {
 		ath9k_eeprom_die "failed to extract from $ubi"
 }
 
+ath9k_eeprom_extract_reverse() {
+	local part=$1
+	local offset=$2
+	local count=$3
+	local mtd
+	local reversed
+	local caldata
+
+	mtd=$(find_mtd_chardev "$part")
+	reversed=$(hexdump -v -s $offset -n $count -e '/1 "%02x "' $mtd)
+
+	for byte in $reversed; do
+		caldata="\x${byte}${caldata}"
+	done
+
+	printf "%b" "$caldata" > /lib/firmware/$FIRMWARE
+}
+
 ath9k_patch_firmware_mac() {
 	local mac=$1
 
@@ -99,6 +117,9 @@ case "$FIRMWARE" in
 		ath9k_eeprom_extract "art" 20480 2048
 		ath9k_patch_firmware_mac $(macaddr_add $(mtd_get_mac_binary art 0) +2)
 		;;
+	fritz300e)
+		ath9k_eeprom_extract_reverse "urloader" 5441 1088
+		;;
 	mr18)
 		. /lib/upgrade/nand.sh