dt: update a reference for reneases pcar file renamed to yaml

dt: update a reference for reneases pcar file renamed to yaml

This file was renamed, but its reference at pfc-pinctl.txt is
still pointing to the old file.

Fixes: 7f7d408e5a00 ("dt-bindings: gpio: rcar: Convert to json-schema")
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/72d7ec91a60e852d34f3e15bc5faef1f62a8260e.1592203542.git.mchehab+huawei@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>