ar71xx-generic: remove CPE220/CPE520 1.0 devices

These devices have never actually existed; the corresponding support
strings have been removed from the stock firmwares as well.

targets/ar71xx-generic

@@ -144,12 +144,10 @@ fi
 
 device tp-link-cpe210-v1.0 cpe210-220
 alias tp-link-cpe210-v1.1
-alias tp-link-cpe220-v1.0
 alias tp-link-cpe220-v1.1
 
 device tp-link-cpe510-v1.0 cpe510-520
 alias tp-link-cpe510-v1.1
-alias tp-link-cpe520-v1.0
 alias tp-link-cpe520-v1.1
 
 device tp-link-wbs210-v1.20 wbs210