can: hi311x: Use level-triggered interrupt

If the hi3110 shares the SPI bus with another traffic-intensive device
and packets are received in high volume (by a separate machine sending
with "cangen -g 0 -i -x"), reception stops after a few minutes and the
counter in /proc/interrupts stops incrementing. Bus state is "active".
Bringing the interface down and back up reconvenes the reception. The
issue is not observed when the hi3110 is the sole device on the SPI bus.

Using a level-triggered interrupt makes the issue go away and lets the
hi3110 successfully receive 2 GByte over the course of 5 days while a
ks8851 Ethernet chip on the same SPI bus handles 6 GByte of traffic.

Unfortunately the hi3110 datasheet is mum on the trigger type. The pin
description on page 3 only specifies the polarity (active high):
http://www.holtic.com/documents/371-hi-3110_v-rev-kpdf.do

Cc: Mathias Duckeck <m.duckeck@kunbus.de>
Cc: Akshay Bhat <akshay.bhat@timesys.com>
Cc: Casey Fitzpatrick <casey.fitzpatrick@timesys.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

dt-bindings: remove 'interrupt-parent' from bindings

'interrupt-parent' is often documented as part of define bindings, but
it is really outside the scope of a device binding. It's never required
in a given node as it is often inherited from a parent node. Or it can
be implicit if a parent node is an 'interrupt-controller' node. So
remove it from all the binding files.

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: devicetree@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>

can: holt_hi311x: document device tree bindings

Document the HOLT HI-311x CAN device tree bindings.

Signed-off-by: Akshay Bhat <nodeax@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>