valgrind: Backport patch to fix build on 4.0 host kernels

Valgrind fails to build when the host kernel is >=4.0. This patch
backports the commit from upstream that fixes the kernel version
verification. This verification is pointless for buildroot anyway, but
it fixes the building process.

[Peter: rename patch to 0002-* and add SoB, slightly reword commit msg]
Signed-off-by: Christian Artin <christian@gridshowsystems.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>