dt-bindings: Correct path for ARM GIC documentation

Commit eb3fcf00 ("dt-bindings: consolidate interrupt controller
bindings") moved the binding documentation for the ARM GIC from
arm/gic.txt to interrupt-controller/arm,gic.txt. However, there are
still some binding documents referring to the old path. Update these
binding documents to use the correct location.

Fixes: eb3fcf00 ("dt-bindings: consolidate interrupt controller bindings")

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Rob Herring <robh@kernel.org>