nios2: Bulk conversion to generic_handle_domain_irq()

Wherever possible, replace constructs that match either
generic_handle_irq(irq_find_mapping()) or
generic_handle_irq(irq_linear_revmap()) to a single call to
generic_handle_domain_irq().
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/nios2/kernel/irq.c

@@ -19,11 +19,9 @@ static u32 ienable;
 asmlinkage void do_IRQ(int hwirq, struct pt_regs *regs)
 {
 	struct pt_regs *oldregs = set_irq_regs(regs);
-	int irq;
 
 	irq_enter();
-	irq = irq_find_mapping(NULL, hwirq);
-	generic_handle_irq(irq);
+	generic_handle_domain_irq(NULL, hwirq);
 	irq_exit();
 
 	set_irq_regs(oldregs);