powercap / RAPL: Floor frequency setting in Atom SoC

CPU Floor frequency is set in BIOS for newer Atom
SoCs. This patch handles configuration of floor
frequency for different variants of Atom SoCs
appropriately and ensures configuration of floor
frequency is not done from driver for these
newer Atom SoCs.

Since address of the register for configuring
floor frequency might change for different
Atom SoCs, this patch also prevents potential
overwriting of wrong registers.

Reviewed-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Ajay Thomas <ajay.thomas.david.rajamanickam@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>