x86, mce: Fix compile warning in case of CONFIG_SMP=n

Fix following compile warning:

  arch/x86/kernel/cpu/mcheck/mce_amd.c: In function 'threshold_create_bank':
  arch/x86/kernel/cpu/mcheck/mce_amd.c:492: warning: unused variable 'c'

which shows up when kernel is compiled with CONFIG_SMP=n.
Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
LKML-Reference: <20090915151727.GB21670@alberich.amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/cpu/mcheck/mce_amd.c

@@ -489,8 +489,9 @@ static __cpuinit int threshold_create_bank(unsigned int cpu, unsigned int bank)
 	int i, err = 0;
 	struct threshold_bank *b = NULL;
 	char name[32];
+#ifdef CONFIG_SMP
 	struct cpuinfo_x86 *c = &cpu_data(cpu);
-
+#endif
 
 	sprintf(name, "threshold_bank%i", bank);