ipq-wifi: add a note / reminder about upstreaming new board files

|Please send a mail with your device-specific board files upstream.
|You can find instructions and examples on the linux-wireless wiki:
|<https://wireless.wiki.kernel.org/en/users/drivers/ath10k/boardfiles>

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>

package/firmware/ipq-wifi/Makefile

@@ -14,6 +14,9 @@ define Build/Compile
 endef
 
 #ALLWIFIBOARDS:=<devicename>
+# Please send a mail with your device-specific board files upstream.
+# You can find instructions and examples on the linux-wireless wiki:
+# <https://wireless.wiki.kernel.org/en/users/drivers/ath10k/boardfiles>
 ALLWIFIBOARDS:=zyxel_nbg6617 zyxel_wre6606
 ALLWIFIPACKAGES:=$(foreach BOARD,$(ALLWIFIBOARDS),ipq-wifi-$(BOARD))