kernel/linux: get kernel version from kernel source

kernel/linux: get kernel version from kernel source

When building the kernel modules, try to get the kernel version from
the kernel sources first.
This fixes the kernel modules installation directory if the target kernel
version differs from the host kernel version, like for CI build or when
packaging for linux distributions.

Signed-off-by: Ferdinand Thiessen <rpm@fthiessen.de>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Tested-by: Ferruh Yigit <ferruh.yigit@intel.com>