cpufreq: arm_big_little: fix module license spec

Having no license specification in a module taints the kernel during load
with:

	arm_big_little: module license 'unspecified' taints kernel.

and also the linker doesn't allow it to make use of GPL-exported symbols
which in this case also results in errors like:

	arm_big_little: Unknown symbol cpufreq_register_driver (err 0)

. The header of the driver specifies a GPL v2 license, so note that
accordingly. While at it also add a description and an author and fix
the license in a companion file to explicit v2.

Reported-by: Andreas Schwab <schwab@suse.de>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>