can: m_can: process interrupt only when not runtime suspended

Avoid processing bogus interrupt statuses when the HW is runtime suspended and
the M_CAN_IR register read may get all bits 1's. Handler can be called if the
interrupt request is shared with other peripherals or at the end of free_irq().

Therefore check the runtime suspended status before processing.

Fixes: cdf8259d65 ("can: m_can: Add PM Support")
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Link: https://lore.kernel.org/r/20200915134715.696303-1-jarkko.nikula@linux.intel.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/m_can/m_can.c

@@ -956,6 +956,8 @@ static irqreturn_t m_can_isr(int irq, void *dev_id)
 	struct net_device_stats *stats = &dev->stats;
 	u32 ir;
 
+	if (pm_runtime_suspended(cdev->dev))
+		return IRQ_NONE;
 	ir = m_can_read(cdev, M_CAN_IR);
 	if (!ir)
 		return IRQ_NONE;