ARC: [SMP] unify cpu private IRQ requests (TIMER/IPI)

The current cpu-private IRQ registration is ugly as it requires need to
expose arch_unmask_irq() outside of intc code.
So switch to percpu IRQ APIs:
  -request_percpu_irq [boot core]
  -enable_percpu_irq  [all cores]

Encapsulated in helper arc_request_percpu_irq()

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

arch/arc/include/asm/irq.h

@@ -16,9 +16,13 @@
 #define TIMER0_IRQ      3
 #define TIMER1_IRQ      4
 
+#include <linux/interrupt.h>
 #include <asm-generic/irq.h>
 
 extern void arc_init_IRQ(void);
 void arc_local_timer_setup(void);
+void arc_request_percpu_irq(int irq, int cpu,
+                            irqreturn_t (*isr)(int irq, void *dev),
+                            const char *irq_nm, void *percpu_dev);
 
 #endif