smp, generic: introduce arch_disable_smp_support() instead of disable_ioapic_setup()

Impact: cleanup

disable_ioapic_setup() in init/main.c is ugly as the function is
x86-specific. The #ifdef inline prototype there is ugly too.

Replace it with a generic arch_disable_smp_support() function - which
has a weak alias for non-x86 architectures and for non-ioapic x86 builds.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/init/main.c b/init/main.c
index bfe4fb0..6441083 100644
--- a/init/main.c
+++ b/init/main.c
@@ -136,14 +136,14 @@
  * greater than 0, limits the maximum number of CPUs activated in
  * SMP mode to <NUM>.
  */
-#ifndef CONFIG_X86_IO_APIC
-static inline void disable_ioapic_setup(void) {};
-#endif
+
+void __weak arch_disable_smp_support(void) { }
 
 static int __init nosmp(char *str)
 {
 	setup_max_cpus = 0;
-	disable_ioapic_setup();
+	arch_disable_smp_support();
+
 	return 0;
 }
 
@@ -153,14 +153,14 @@
 {
 	get_option(&str, &setup_max_cpus);
 	if (setup_max_cpus == 0)
-		disable_ioapic_setup();
+		arch_disable_smp_support();
 
 	return 0;
 }
 
 early_param("maxcpus", maxcpus);
 #else
-#define setup_max_cpus NR_CPUS
+const unsigned int setup_max_cpus = NR_CPUS;
 #endif
 
 /*