kni: use utsrelease to determine Ubuntu kernel version

kni: use utsrelease to determine Ubuntu kernel version

/proc/version_signature is the version for the host machine, but in
e.g., chroots, this does not necessarily match that DPDK is built
for. DPDK will then build for the wrong kernel version - that of the
server, and not that installed in the (build) chroot.

The patch uses utsrelease.h from the kernel sources instead and fakes
the upload version.

Tested on a server with Ubuntu 12.04, building in a chroot for Ubuntu
14.04.

Signed-off-by: Simon Kagstrom <simon.kagstrom@netinsight.net>
Signed-off-by: Johan Faltstrom <johan.faltstrom@netinsight.net>
Acked-by: Helin Zhang <helin.zhang@intel.com>