clocksource/timer-riscv: Add riscv_clock_shutdown callback

Add clocksource detach/shutdown callback to disable RISC-V timer interrupt when
switching out riscv timer as clock source

Signed-off-by: Joshua Yeong <joshua.yeong@starfivetech.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20231116105312.4800-1-joshua.yeong@starfivetech.com

drivers/clocksource/timer-riscv.c

@@ -61,12 +61,19 @@ static int riscv_clock_next_event(unsigned long delta,
 	return 0;
 }
 
+static int riscv_clock_shutdown(struct clock_event_device *evt)
+{
+	riscv_clock_event_stop();
+	return 0;
+}
+
 static unsigned int riscv_clock_event_irq;
 static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
 	.name			= "riscv_timer_clockevent",
 	.features		= CLOCK_EVT_FEAT_ONESHOT,
 	.rating			= 100,
 	.set_next_event		= riscv_clock_next_event,
+	.set_state_shutdown	= riscv_clock_shutdown,
 };
 
 /*