irqchip/gic: Work around broken Renesas integration

[ Upstream commit b78f2692 ]

Geert reported that the GIC driver locks up on a Renesas system
since 005c34ae ("irqchip/gic: Atomically update affinity")
fixed the driver to use writeb_relaxed() instead of writel_relaxed().

As it turns out, the interconnect used on this system mandates
32bit wide accesses for all MMIO transactions, even if the GIC
architecture specifically mandates for some registers to be byte
accessible. Gahhh...

Work around the issue by crudly detecting the offending system,
and falling back to an inefficient RMW+lock implementation.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/CAMuHMdV+Ev47K5NO8XHsanSq5YRMCHn2gWAQyV-q2LpJVy9HiQ@mail.gmail.com


Signed-off-by: Sasha Levin <sashal@kernel.org>