RISC-V: Remove do_IRQ() function

The only thing do_IRQ() does is call handle_arch_irq function
pointer. We can very well call handle_arch_irq function pointer
directly from assembly and remove do_IRQ() function hence this
patch.
Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/kernel/entry.S

@@ -106,7 +106,9 @@ _save_context:
 
 	/* Handle interrupts */
 	move a0, sp /* pt_regs */
-	tail do_IRQ
+	la a1, handle_arch_irq
+	REG_L a1, (a1)
+	jr a1
 1:
 	/*
 	 * Exceptions run with interrupts enabled or disabled depending on the

arch/riscv/kernel/irq.c

@@ -16,12 +16,6 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 	return 0;
 }
 
-asmlinkage __visible void __irq_entry do_IRQ(struct pt_regs *regs)
-{
-	if (handle_arch_irq)
-		handle_arch_irq(regs);
-}
-
 void __init init_IRQ(void)
 {
 	irqchip_init();