remoteproc: pru: Fixup interrupt-parent logic for fw events

remoteproc: pru: Fixup interrupt-parent logic for fw events

The PRU firmware interrupt mapping logic in pru_handle_intrmap() uses
of_irq_find_parent() with PRU device node to get a handle to the PRUSS
Interrupt Controller at present. This logic however requires that the
PRU nodes always define a interrupt-parent property. This property is
neither a required/defined property as per the PRU remoteproc binding,
nor is relevant from a DT node point of view without any associated
interrupts. The current logic finds a wrong interrupt controller and
fails to perform proper mapping without any interrupt-parent property
in the PRU nodes.

Fix this logic to always find and use the sibling interrupt controller.
Also, while at this, fix the acquired interrupt controller device node
reference properly.

Fixes: c75c9fdac66e ("remoteproc: pru: Add support for PRU specific interrupt configuration")
Signed-off-by: Suman Anna <s-anna@ti.com>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20210407155641.5501-2-s-anna@ti.com
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>