linux-headers: resync from mainline to add ARM KVM headers

linux-headers: resync from mainline to add ARM KVM headers

Resync QEMU's copy of the Linux kernel headers from
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
commit 2ef14f4. This adds the ARM KVM headers, since ARM KVM
support has just hit mainline via Russell's ARM tree.

This is not a pure sync -- I have removed by hand some changes
that would have reverted updates for s390x and ppc which have not
yet hit mainline.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>