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>

Input: add support for NI Ettus Research USRP E3x0 button

Signed-off-by: Moritz Fischer <moritz.fischer@ettus.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>