cr-service: fix return result for not supported cpuinfo

The change to fill out cr_errno if cpuinfo dump/check failed
in the previous patch 7e862bb3
was returning (-ENOTSUP & 0xff). To easier check for
the return result this is now changed to just return ENOTSUP.

Signed-off-by: Adrian Reber <areber@redhat.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>