x86: move smp_ops extern declaration to common header

the smp_ops symbol is temporarily defined in smp_64.c, but it will soon
be unified

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/asm-x86/smp.h b/include/asm-x86/smp.h
index d11b92b..ee98bee 100644
--- a/include/asm-x86/smp.h
+++ b/include/asm-x86/smp.h
@@ -21,6 +21,9 @@
 				      int wait);
 };
 
+#ifdef CONFIG_SMP
+extern struct smp_ops smp_ops;
+#endif
 
 #ifdef CONFIG_X86_32
 # include "smp_32.h"