drivers: misc: irq-uclass: Update irq_get_by_index

drivers: misc: irq-uclass: Update irq_get_by_index

Support reading the "interrupts" property from the devicetree in case
the "interrupts-extended" property isn't found. As the "interrupts"
property is commonly used, this allows to parse all existing FDT and
makes irq_get_by_index() more useful.

The "interrupts" property doesn't contain a phandle as "interrupts-extended"
does, so implement a new method to locate the interrupt-parent called
irq_get_interrupt_parent().

TEST: Read the interrupts from the GIC node for ACPI MADT generation.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-by: Moritz Fischer <moritzf@google.com>