version.h is included but not used by per_cpu.h. This results in a forceful
rebuild of almost all files because per_cpu.h (and thus version.h) is depended
on by many files, and version.h is created every time a build is triggered.
This patch breaks this dependency. No further changes needed as sources using
version.h all include that file explicitly.
Also add the missing license header BTW.
Signed-off-by: Junjie Mao <junjie.mao@intel.com>