x86/irq: Use generic irq_regs implementation

The only difference is the name of the per-CPU variable: irq_regs
vs. __irq_regs, but the accessor functions are identical.

Remove the pointless copy and use the generic variant.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20200521202118.704169051@linutronix.de

Author: KAGA-KOKO

arch/x86/include/asm/irq_regs.h

@@ -26,9 +26,6 @@
 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);
-
 atomic_t irq_err_count;
 
 /*