ar71xx: add TP-LINK TL-WR841N/ND v12 image

This router has the same hardware as TP-LINK TL-WR841N/ND v11 (same FCC
ID, same TFTP image name...).

If the stock firmware web interface doesn't accept LEDE factory image,
it can be flashed via the U-Boot TFTP recovery mode, by long-pressing
the reset button after power on.

The TFTP image name is wr841nv11_tp_recovery.bin (yes, v11, not v12).

Signed-off-by: Vittorio Gambaletta <openwrt@vittgam.net>

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

@@ -736,6 +736,12 @@ define Device/tl-wr841-v11
   IMAGE/factory-eu.bin := append-rootfs | mktplinkfw factory -C EU
 endef
 
+define Device/tl-wr841-v12
+  $(Device/tl-wr841-v11)
+  DEVICE_TITLE := TP-LINK TL-WR841N/ND v12
+  TPLINK_HWID := 0x08410012
+endef
+
 define Device/tl-wr842n-v1
   $(Device/tplink-8m)
   DEVICE_TITLE := TP-LINK TL-WR842N/ND v1
@@ -778,7 +784,7 @@ define Device/tl-wr847n-v8
   DEVICE_PROFILE := TLWR841
   TPLINK_HWID := 0x08470008
 endef
-TARGET_DEVICES += tl-wr840n-v2 tl-wr840n-v3 tl-wr841-v1.5 tl-wr841-v3 tl-wr841-v5 tl-wr841-v7 tl-wr841-v8 tl-wr841-v9 tl-wr841-v10 tl-wr841-v11 tl-wr842n-v1 tl-wr842n-v2 tl-wr842n-v3 tl-wr843nd-v1 tl-wr847n-v8
+TARGET_DEVICES += tl-wr840n-v2 tl-wr840n-v3 tl-wr841-v1.5 tl-wr841-v3 tl-wr841-v5 tl-wr841-v7 tl-wr841-v8 tl-wr841-v9 tl-wr841-v10 tl-wr841-v11 tl-wr841-v12 tl-wr842n-v1 tl-wr842n-v2 tl-wr842n-v3 tl-wr843nd-v1 tl-wr847n-v8
 
 define Device/tl-wr941nd-v2
   $(Device/tplink-4m)