Oprofile: Change CPUIDS from decimal to hex, and add some comments

Back when the patch was submitted for "Add Xeon 7500 series support to
oprofile", Robert Richter had asked for a followon patch that
converted all the CPU ID values to hex.

I have done that here for the "i386/core_i7" and "i386/atom" class
processors in the ppro_init() function and also added some comments on
where to find documentation on the Intel processors.

Signed-off-by: John L. Villalovos <john.l.villalovos@intel.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>