ath79: add support for MikroTik RouterBOARD 922UAGS-5HPacD

This patch ports support for the MikroTik RouterBOARD 922UAGS-5HPacD
with a built-in 802.11ac High-Power radio (31dBm), which was already
available in the ar71xx target.

See https://mikrotik.com/product/RB922UAGS-5HPacD for more info.

Specifications:
- SoC: Qualcomm Atheros QCA9558 (720 MHz)
- RAM: 128 MB
- Storage: 128 MB NAND
- Wireless: external QCA9882 802.11a/ac 2x2:2
- Ethernet: 1x 1000/100/10 Mbps, integrated, via AR8031 PHY, passive PoE-in 24V
- SFP: 1x host
- USB: 1x 2.0 type A
- PCIe: 1x Mini slot (also contains USB 2.0 for 3G/LTE modems)
- SIM slot: 1x mini-SIM

Working:
- Board/system detection
- SPI and NAND storage
- PCIe
- USB type A host
- Wireless
- Ethernet
- LEDs (user, phy0)
- Reset button
- Sysupgrade to/from ar71xx

Not supported:
- RSSI LEDs
- SFP cage

Installation methods:
- Sysupgrade from ar71xx (it is advisable to use the -n option to
wipe any previous settings), or
- Boot the initramfs image via TFTP and then flash the sysupgrade
image using "sysupgrade -n"

Signed-off-by: Roger Pueyo Centelles <roger.pueyo@guifi.net>

target/linux/ath79/nand/base-files/lib/upgrade/platform.sh

@@ -7,13 +7,27 @@ platform_check_image() {
 	return 0
 }
 
-RAMFS_COPY_BIN='fw_printenv fw_setenv'
+RAMFS_COPY_BIN='fw_printenv fw_setenv nandwrite'
 RAMFS_COPY_DATA='/etc/fw_env.config /var/lock/fw_printenv.lock'
 
+platform_do_upgrade_mikrotik_nand() {
+	CI_KERNPART=none
+	local fw_mtd=$(find_mtd_part kernel)
+	fw_mtd="${fw_mtd/block/}"
+	[ -n "$fw_mtd" ] || return
+	mtd erase kernel
+	tar xf "$1" sysupgrade-routerboard/kernel -O | nandwrite -o "$fw_mtd" -
+
+	nand_do_upgrade "$1"
+}
+
 platform_do_upgrade() {
 	local board=$(board_name)
 
 	case "$board" in
+	mikrotik,routerboard-922uags-5hpacd)
+		platform_do_upgrade_mikrotik_nand "$1"
+		;;
 	glinet,gl-ar300m-nand|\
 	glinet,gl-ar300m-nor)
 		glinet_nand_nor_do_upgrade "$1"