cpufreq: scpi: remove stale/outdated comment about the driver

Commit 343a8d17 ("cpufreq: scpi: remove arm_big_little dependency")
removed the arm_big_little dependency from scpi driver and doesn't
provide any ops to arm_big_little cpufreq driver. Lets remove that
stale comment.

Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>