asm-generic: drop HARDIRQ_BITS definition from hardirq.h

Architechtures normally don't need to set a HARDIRQ_BITS
unless they have hardcoded a specific value in assembly.
This drops the definition from asm-generic/hardirq.h, which
results in linux/hardirq.h setting its default of 10.

Both the old default of 8 and the linux/hardirq.h default
of 10 are sufficient because they only limit the number
of nested hardirqs, and we normally run out of stack space
much earlier than exceeding 256 or even 1024 nested interrupts.

Reported-by: Mike Frysinger <vapier@gentoo.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

include/asm-generic/hardirq.h

@@ -11,19 +11,6 @@ typedef struct {
 
 #include <linux/irq_cpustat.h>	/* Standard mappings for irq_cpustat_t above */
 
-#ifndef HARDIRQ_BITS
-#define HARDIRQ_BITS	8
-#endif
-
-/*
- * The hardirq mask has to be large enough to have
- * space for potentially all IRQ sources in the system
- * nesting on a single CPU:
- */
-#if (1 << HARDIRQ_BITS) < NR_IRQS
-# error HARDIRQ_BITS is too low!
-#endif
-
 #ifndef ack_bad_irq
 static inline void ack_bad_irq(unsigned int irq)
 {