mixtile-blade3: board: disable 'edge' kernel, as it's not ready for end-users yet

- one can still build and try with `BRANCH=edge` forced
- but mainline is simply not ready for this yet
- help wanted!

Author: rpardini

config/boards/mixtile-blade3.csc

@@ -3,7 +3,7 @@ declare -g BOARD_NAME="Mixtile Blade 3"
 declare -g BOARD_VENDOR="mixtile"
 declare -g BOARDFAMILY="rockchip-rk3588"
 declare -g BOARD_MAINTAINER="rpardini"
-declare -g KERNEL_TARGET="vendor,edge"
+declare -g KERNEL_TARGET="vendor"                                # edge builds and can be used for development with 'BRANCH=edge` forced; not enabled for end-users
 declare -g BOOT_FDT_FILE="rockchip/rk3588-blade3-v101-linux.dtb" # Included in https://github.com/armbian/linux-rockchip/pull/64 # has a hook to change it for edge below
 declare -g BOOT_SCENARIO="spl-blobs"                             # so we don't depend on defconfig naming convention
 declare -g BOOT_SOC="rk3588"                                     # so we don't depend on defconfig naming convention