x86: merge irq_regs.h

Impact: cleanup, better irq_regs code generation for x86_64

Make 64-bit use the same optimizations as 32-bit.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

arch/x86/kernel/irq_64.c

@@ -22,6 +22,9 @@
 DEFINE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
 EXPORT_PER_CPU_SYMBOL(irq_stat);
 
+DEFINE_PER_CPU(struct pt_regs *, irq_regs);
+EXPORT_PER_CPU_SYMBOL(irq_regs);
+
 /*
  * Probabilistic stack overflow check:
  *