treewide: revert sysupgrade adjustments for early DSA-adopters

The uci-default mechanism to update the compat-version was only
meant for early DSA-adopters, which should have updated by now.

Remove this workaround again in order to prevent the intended
experiences for all the other people.

This reverts:
a9703db72030 ("mvebu: fix sysupgrade experience for early DSA-adopters")
86c89bf5e8f5 ("kirkwood: fix sysupgrade experience for early DSA-adopters")

Partially reverted:
1eac573b5304 ("ramips: mt7621: implement compatibility version for DSA migration")

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/kirkwood/base-files/etc/uci-defaults/05_fix-compat-version

@@ -1,16 +0,0 @@
-#
-# Copyright (C) 2020 OpenWrt.org
-#
-
-. /lib/functions.sh
-
-case "$(board_name)" in
-	linksys,e4200-v2|\
-	linksys,ea3500|\
-	linksys,ea4500)
-		uci set system.@system[0].compat_version="1.1"
-		uci commit system
-		;;
-esac
-
-exit 0

target/linux/mvebu/cortexa9/base-files/etc/uci-defaults/05_fix-compat-version

@@ -1,21 +0,0 @@
-#
-# Copyright (C) 2020 OpenWrt.org
-#
-
-. /lib/functions.sh
-
-case "$(board_name)" in
-	linksys,wrt1200ac|\
-	linksys,wrt1900ac-v1|\
-	linksys,wrt1900ac-v2|\
-	linksys,wrt1900acs|\
-	linksys,wrt3200acm|\
-	linksys,wrt32x|\
-	solidrun,clearfog-base-a1|\
-	solidrun,clearfog-pro-a1)
-		uci set system.@system[0].compat_version="1.1"
-		uci commit system
-		;;
-esac
-
-exit 0

target/linux/ramips/mt7621/base-files/etc/uci-defaults/05_fix-compat-version

@@ -1,8 +0,0 @@
-#
-# Copyright (C) 2020 OpenWrt.org
-#
-
-uci set system.@system[0].compat_version="1.1"
-uci commit system
-
-exit 0