This adds the cpus node to the Integrator/AP device tree so
that we have a proper placeholder to put in the DT-defined
operating points for the generic DT/OPP cpufreq driver,
along with the proper operating points.

The old Integrator cpufreq driver would resolve the max
frequency to 71MHz, and the min frequency to 12 MHz, but
the clock driver can actually handle any frequency inbetween
so I picked a few select frequencies as OPPs. The cpufreq
framework doesn't seem to deal with sliding frequency scales,
only fixed points so 7 OPPs is better than 2 atleast.

We define a CPU node since this is required for cpufreq-dt,
however we do not define any compatible string for the CPU
since this architecture has pluggable CPU modules and we
do not know which one will be used. If necessary, the CPU
compatible can be filled in by the boot loader, but for
just cpufreq-dt it is not required.

Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>