x86: make 64bit have get_apic_id

generalize the x2apic code some more.

let read_apic_id become a macro (later on a function/inline)
GET_APIC_ID(apic_read(APIC_ID))

  +#define read_apic_id()  (GET_APIC_ID(apic_read(APIC_ID)))

instead of this weird construct:

  -#define read_apic_id  (genapic->read_apic_id)

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/asm-x86/mach-default/mach_apic.h b/include/asm-x86/mach-default/mach_apic.h
index 925b797..3d2b455 100644
--- a/include/asm-x86/mach-default/mach_apic.h
+++ b/include/asm-x86/mach-default/mach_apic.h
@@ -30,7 +30,7 @@
 #define cpu_mask_to_apicid (genapic->cpu_mask_to_apicid)
 #define phys_pkg_id	(genapic->phys_pkg_id)
 #define vector_allocation_domain    (genapic->vector_allocation_domain)
-#define read_apic_id  (genapic->read_apic_id)
+#define read_apic_id()  (GET_APIC_ID(apic_read(APIC_ID)))
 #define send_IPI_self (genapic->send_IPI_self)
 extern void setup_apic_routing(void);
 #else