irqchip/gic-v3-its: Handle non-coherent GICv4 redistributors

Although the GICv3 code base has gained some handling of systems failing to
handle the shareability attributes, the GICv4 side of things has been
firmly ignored.

This is unfortunate, as the new recent addition of the "dma-noncoherent" is
supposed to apply to all of the GICR tables, and not just the ones that are
common to v3 and v4.

Add some checks to handle the VPROPBASE/VPENDBASE shareability and
cacheability attributes in the same way we deal with the other GICR_BASE
registers, wrapping the flag check in a helper for improved readability.

Note that this has been found by inspection only, as I don't have access to
HW that suffers from this particular issue.

Fixes: 3a0fff0f ("irqchip/gic-v3: Enable non-coherent redistributors/ITSes DT probing")
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Link: https://lore.kernel.org/r/20240213101206.2137483-2-maz@kernel.org