Create the bbappend for v6.6 and bump the default kernel to v6.6 for
all the machines.
In the v6.6 kernel the dtb files for beaglebone have been moved to a
vendor specific directory, so we also need to adjust the corresponding
variables for its DTB generation.
(From meta-yocto rev: 58ac51b7a44fbb165311c7226ae8b15cd004114d)
Signed-off-by: Kevin Hao <kexin.hao@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>