cpuidle: License cleanup

Len!

As you might know we are working on cleaning up the licensing mess in the
kernel and convert it to SPDX license identifiers as the only source of
license information.

Archaeology found unspecific GPL license references, which have been
authored/comitted by you.

Pattern: This code is licenced under the GPL

    drivers/cpuidle/cpuidle.c
    drivers/cpuidle/driver.c
    drivers/cpuidle/governor.c
    drivers/cpuidle/sysfs.c
    drivers/cpuidle/governors/ladder.c
    include/linux/cpuidle.h

Can you please either send cleanup patches for the affected files or
indicate which GPLv2 variant you had in mind and I run it through my
cleanup machinery.

Thanks,

	Thomas