lscpu: use GPLv2+

lscpu: use GPLv2+

CAI Qian and I agree that GPLv2+ is better for lscpu.c. This license
is more compatible (than v3) with the rest of the util-linux package.
We need to link the code with functions from lib/ -- mix GPLv3 and
GPLv2 is bad idea.

Note that it was only Cai and I who did significant changes to
lscpu.c, all others changes from others developers was trivial (fix
typos, add _(), ...).

Signed-off-by: CAI Qian <caiqian@redhat.com>
Signed-off-by: Karel Zak <kzak@redhat.com>