x86/oprofile: introduce model specific init/exit functions

This patch implements model specific OProfile init/exit functions for
x86 CPUs. Though there is more rework needed at the initialization
code, this new introduced functions allow it to keep model specific
code in the corresponding op_model_*.c files.

The function interface is the same as for oprofile_arch_init/exit().

Signed-off-by: Robert Richter <robert.richter@amd.com>
Cc: oprofile-list <oprofile-list@lists.sourceforge.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>