x86: common.c declare idle_regs before they get used

Signed-off-by: Jaswinder Singh <jaswinder@infradead.org>

include/asm-x86/processor.h

@@ -155,6 +155,8 @@ static inline int hlt_works(int cpu)
 
 extern void cpu_detect(struct cpuinfo_x86 *c);
 
+extern struct pt_regs *idle_regs(struct pt_regs *);
+
 extern void early_cpu_init(void);
 extern void identify_boot_cpu(void);
 extern void identify_secondary_cpu(struct cpuinfo_x86 *);