ipq806x: convert to dt-based board-detection

Use the generic board detection method:
- Board name: First compatible string from the device tree
- Board model: Model property from the device tree

Change occurrences of board name in userspace by the compatible
string, and removed target specific board detection script

Replace the definition of SUPPORTED_DEVICES in Device/Default
to extract the dt compatible string from each device definition.
Additionally, for devices supported by lede-17.01, append
the value of BOARD_NAME to SUPPORTED_DEVICES in the device
definition.

Signed-off-by: Luis Araneda <luaraneda@gmail.com>

package/boot/uboot-envtools/files/ipq

@@ -31,13 +31,14 @@ ubootenv_mtdinfo () {
 }
 
 case "$board" in
-ap148 | db149)
+qcom,ipq8064-ap148 |\
+qcom,ipq8064-db149)
 	ubootenv_add_uci_config $(ubootenv_mtdinfo)
 	;;
-ea8500)
+linksys,ea8500)
 	ubootenv_add_uci_config "/dev/mtd10" "0x0" "0x20000" "0x20000"
 	;;
-nbg6817)
+zyxel,nbg6817)
 	ubootenv_add_uci_config "/dev/mtdblock9" "0x0" "0x10000" "0x10000"
 	;;
 esac