'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 <email@example.com>
Signed-off-by: Rob Herring <firstname.lastname@example.org>