cpufreq: probe the Integrator cpufreq driver from DT

This makes the Integrator cpufreq driver probe from the core
module device tree node through it's registered platforms
device, getting the memory base from the device tree,
remapping it and removing dependencies to <mach/platform.h>
and <mach/hardware.h> by moving the two affected CM
register offsets into the driver.

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>