ARM: vexpress/TC2: register vexpress-spc cpufreq device

This patch adds vexpress-spc platform device to enables the vexpress
SPC cpufreq interface driver.

Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
Acked-by: Pawel Moll <Pawel.Moll@arm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>