x86/apic/32: Remove x86_cpu_to_logical_apicid

x86/apic/32: Remove x86_cpu_to_logical_apicid

This per CPU variable is just yet another form of voodoo programming. The
boot ordering is:

  per_cpu(x86_cpu_to_logical_apicid, cpu) = 1U << cpu;

  .....

  setup_apic()
     apic->init_apic_ldr()
       default_init_apic_ldr()
         apic_write(SET_APIC_LOGICAL_ID(1UL << smp_processor_id(), APIC_LDR);

     id = GET_APIC_LOGICAL_ID(apic_read(APIC_LDR);
     WARN_ON(id != per_cpu(x86_cpu_to_logical_apicid, cpu));
     per_cpu(x86_cpu_to_logical_apicid, cpu) = id;

So first write the default into LDR and then validate it against the same default
which was set up during early boot APIC enumeration.

Brilliant, isn't it?

The comment above the per CPU variable declaration describes it well:
'Let's keep it ugly for now.'

Remove the useless gunk and use '1U << cpu' consistently all over the place.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Tested-by: Juergen Gross <jgross@suse.com> # Xen PV (dom0 and unpriv. guest)