kbuild: Bump the build system to 6.1

kbuild: Bump the build system to 6.1

Our last sync with the kernel was 5.1.

We are so out of sync now, that tracking the patches and backporting
them one by one makes little sense and it's going to take ages.

This is an attempt to sync up Makefiles to 6.1.
Unfortunately due to sheer amount of patches this is not easy to review,
but that's what we decided during a community call for the bump to 5.1,
so we are following the same guidelines here.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>a #rebased on -next