ar71xx: image: specify TPLINK_HWID for TP-Link RE450

TPLINK_HWID hasn't been specified for TP-Link RE450 since the begin.
As we don't want to break sysupgrade (all existing LEDE release images
for this board have TPLINK_HWID set to 0x0), set it explicitly to 0x0.

Fixes FS#852

Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>

target/linux/ar71xx/image/tp-link.mk

@@ -282,6 +282,7 @@ define Device/re450-v1
   TPLINK_BOARD_ID := RE450
   DEVICE_PROFILE := RE450
   LOADER_TYPE := elf
+  TPLINK_HWID := 0x0
   KERNEL := kernel-bin | patch-cmdline | lzma | mktplinkfw-kernel
   IMAGES := sysupgrade.bin factory.bin
   IMAGE/sysupgrade.bin := append-rootfs | tplink-safeloader sysupgrade