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>

target/linux/ipq806x/base-files/etc/init.d/linksys_recovery

@@ -6,7 +6,7 @@ boot() {
 . /lib/functions.sh
 
 case $(board_name) in
-	ea8500)
+	linksys,ea8500)
 		# make sure auto_recovery in uboot is always on
 		AUTO_RECOVERY_ENA="`fw_printenv -n auto_recovery`"
 		if [ "$AUTO_RECOVERY_ENA" != "yes" ] ; then