MIPS: octeon: Remove ARCH_HAS_IRQ_PER_CPU

ARCH_HAS_IRQ_PER_CPU is unused anywhere in the kernel - remove the
definition.
Signed-off-by: Paul Burton <paul.burton@mips.com>

arch/mips/include/asm/mach-cavium-octeon/cpu-feature-overrides.h

@@ -59,7 +59,6 @@
 
 #define cpu_has_rixi		(cpu_data[0].cputype != CPU_CAVIUM_OCTEON)
 
-#define ARCH_HAS_IRQ_PER_CPU	1
 #define ARCH_HAS_SPINLOCK_PREFETCH 1
 #define spin_lock_prefetch(x) prefetch(x)
 #define PREFETCH_STRIDE 128