irqstat: Move declaration into asm-generic/hardirq.h

Move the declaration of the irq_cpustat per cpu variable to
asm-generic/hardirq.h and remove the now empty linux/irq_cpustat.h header.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20201113141733.737377332@linutronix.de

include/asm-generic/hardirq.h

@@ -12,7 +12,8 @@ typedef struct {
 #endif
 } ____cacheline_aligned irq_cpustat_t;
 
-#include <linux/irq_cpustat.h>	/* Standard mappings for irq_cpustat_t above */
+DECLARE_PER_CPU_ALIGNED(irq_cpustat_t, irq_stat);
+
 #include <linux/irq.h>
 
 #ifndef ack_bad_irq

include/linux/irq_cpustat.h

-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef __irq_cpustat_h
-#define __irq_cpustat_h
-
-/*
- * Contains default mappings for irq_cpustat_t, used by almost every
- * architecture.  Some arch (like s390) have per cpu hardware pages and
- * they define their own mappings for irq_stat.
- *
- * Keith Owens <kaos@ocs.com.au> July 2000.
- */
-
-
-/*
- * Simple wrappers reducing source bloat.  Define all irq_stat fields
- * here, even ones that are arch dependent.  That way we get common
- * definitions instead of differing sets for each arch.
- */
-
-#ifndef __ARCH_IRQ_STAT
-DECLARE_PER_CPU_ALIGNED(irq_cpustat_t, irq_stat);	/* defined in asm/hardirq.h */
-#endif
-
-#endif	/* __irq_cpustat_h */