mrf24j40: Use level-triggered interrupts

The mrf24j40 generates level interrupts. There are rare cases where it
appears that the interrupt line never gets de-asserted between interrupts,
causing interrupts to be lost, and causing a hung device from the driver's
perspective.  Switching the driver to interpret these interrupts as
level-triggered fixes this issue.

Signed-off-by: Alan Ott <alan@signal11.us>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ieee802154/mrf24j40.c b/drivers/net/ieee802154/mrf24j40.c
index c1bc688..0632d34 100644
--- a/drivers/net/ieee802154/mrf24j40.c
+++ b/drivers/net/ieee802154/mrf24j40.c
@@ -678,7 +678,7 @@
 	ret = request_threaded_irq(spi->irq,
 				   NULL,
 				   mrf24j40_isr,
-				   IRQF_TRIGGER_FALLING|IRQF_ONESHOT,
+				   IRQF_TRIGGER_LOW|IRQF_ONESHOT,
 				   dev_name(&spi->dev),
 				   devrec);