RISC-V: simplify software interrupt / IPI code

Rename handle_ipi to riscv_software_interrupt, drop the unused return
value and move the prototype to irq.h together with riscv_timer_interupt.
This allows simplifying the upcoming interrupt handling support.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 6d39624..906fe21 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -45,7 +45,7 @@ int setup_profiling_timer(unsigned int multiplier)
 	return -EINVAL;
 }
 
-irqreturn_t handle_ipi(void)
+void riscv_software_interrupt(void)
 {
 	unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits;
 
@@ -60,7 +60,7 @@ irqreturn_t handle_ipi(void)
 
 		ops = xchg(pending_ipis, 0);
 		if (ops == 0)
-			return IRQ_HANDLED;
+			return;
 
 		if (ops & (1 << IPI_RESCHEDULE))
 			scheduler_ipi();
@@ -73,8 +73,6 @@ irqreturn_t handle_ipi(void)
 		/* Order data access and bit testing. */
 		mb();
 	}
-
-	return IRQ_HANDLED;
 }
 
 static void