[IA64] /proc/cpuinfo "physical id" field cleanups

Clean up the process for presenting the "physical id" field in
/proc/cpuinfo.

	- remove global smp_num_cpucores, as it is mostly useless

	- remove check_for_logical_procs(), since we do the same
	  functionality in identify_siblings()

	- reflow logic in identify_siblings(). If an older CPU
	  does not implement PAL_LOGICAL_TO_PHYSICAL, we may still
	  be able to get useful information from SAL_PHYSICAL_ID_INFO

	- in identify_siblings(), threads/cores are a property of
	  the CPU, not the platform

	- remove useless printk's about multi-core / thread
	  capability in identify_siblings(), as that information
	  is readily available in /proc/cpuinfo, and printing for
	  the BSP only adds little value

	- smp_num_siblings is now meaningful if any CPU in the
	  system supports threads, not just the BSP

	- expose "physical id" field, even on CPUs that are not
	  multi-core / multi-threaded (as long as we have a valid
	  value). Now we know what sockets Madisons live in too.

Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>