iio: imu: inv_mpu6050: Fix probe() failure on older ACPI based machines

Commit 5ec6486daa98 ("iio:imu: inv_mpu6050: support more interrupt types")
causes inv_mpu_core_probe() to fail if the IRQ does not have a
trigger-type setup.

This happens on machines where the mpu6050 is enumerated through ACPI and
an older Interrupt type ACPI resource is used for the interrupt, rather
then a GpioInt type type, causing the mpu6050 driver to no longer work
there. This happens on e.g. the Asus T100TA.

This commits makes the mpu6050 fallback to the old IRQF_TRIGGER_RISING
default if the irq-type is not setup, fixing this.

Signed-off-by: Hans de Goede <[e-mail]>
Fixes: 5ec6486daa98 ("iio:imu: inv_mpu6050: support more interrupt types")
Reviewed-by: Martin Kelly <[e-mail]>
Reviewed-by: Jean-Baptiste Maneyrol <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/imu/inv_mpu6050/inv_mpu_core.c

···
 	}
 
 	irq_type = irqd_get_trigger_type(desc);
+	if (!irq_type)
+		irq_type = IRQF_TRIGGER_RISING;
 	if (irq_type == IRQF_TRIGGER_RISING)
 		st->irq_mask = INV_MPU6050_ACTIVE_HIGH;
 	else if (irq_type == IRQF_TRIGGER_FALLING)