[ARM] give RiscPC a NR_IRQS definition and remove default

RiscPC is the only platform using the default setting for NR_IRQS,
so the default NR_IRQS doesn't really make sense; remove it and
make RiscPC provide such a definition.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/irq.h

@@ -7,10 +7,6 @@
 #define irq_canonicalize(i)	(i)
 #endif
 
-#ifndef NR_IRQS
-#define NR_IRQS	128
-#endif
-
 /*
  * Use this value to indicate lack of interrupt
  * capability

arch/arm/mach-rpc/include/mach/irqs.h

@@ -44,3 +44,4 @@
 
 #define IRQ_TIMER		IRQ_TIMER0
 
+#define NR_IRQS			128