base-files are added into subtarget directory like what's done
recently in ath79. For this subtarget, metadata checks are enforced
and a SUPPORTED_DEVICE is added to generate proper metadata.
Since we only have mt7629 support in 4.19, override KERNEL_PATCHVER
in target.mk for now.
Signed-off-by: Chuanhong Guo <gch981213@gmail.com>