irqchip/gicv3: Workaround for Cavium ThunderX erratum 23154

This patch implements Cavium ThunderX erratum 23154.

The gicv3 of ThunderX requires a modified version for reading the IAR
status to ensure data synchronization. Since this is in the fast-path
and called with each interrupt, runtime patching is used using jump
label patching for smallest overhead (no-op). This is the same
technique as used for tracepoints.

Signed-off-by: Robert Richter <rrichter@cavium.com>
Reviewed-by: Marc Zygnier <marc.zyngier@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Tirumalesh Chalamarla <tchalamarla@cavium.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/1442869119-1814-3-git-send-email-rric@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>