buildroot

defconfigs: use the new headers-version-same-as-kernel-version option

Now that we can say that the linux headers version should match that of
the kernel to be built, we inverse the logic in our defconfigs, as it is
more sensible that way.

And also because we'll get rid of the former, converse kernel-same-as-headers
option.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>