ARC: smp: Introduce smp hook @init_irq_cpu called for all cores

Note this is not part of platform owned static machine_desc,
but more of device owned plat_smp_ops (rather misnamed) which a IPI
provider or some such typically defines.

This will help us seperate out the IPI registration from platform
specific init_cpu_smp() into device specific init_irq_cpu()

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/kernel/irq.c

@@ -10,6 +10,7 @@
 #include <linux/interrupt.h>
 #include <linux/irqchip.h>
 #include <asm/mach_desc.h>
+#include <asm/smp.h>
 
 /*
  * Late Interrupt system init called from start_kernel for Boot CPU only
@@ -27,7 +28,10 @@ void __init init_IRQ(void)
 	irqchip_init();
 
 #ifdef CONFIG_SMP
-	/* Master CPU can initialize it's side of IPI */
+	/* a SMP H/w block could do IPI IRQ request here */
+	if (plat_smp_ops.init_irq_cpu)
+		plat_smp_ops.init_irq_cpu(smp_processor_id());
+
 	if (machine_desc->init_cpu_smp)
 		machine_desc->init_cpu_smp(smp_processor_id());
 #endif