dts: bindings: ensure bindings have .yaml extension (not .yml)

Strictly speaking not a problem for in-tree tooling, but better to
have all binding files follow the same naming convention.

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>

Author: kartben

dts/bindings/clock/renesas,rz-cpg.yml renamed to dts/bindings/clock/renesas,rz-cpg.yaml

@@ -4,4 +4,4 @@
 description: RZ/A2M Clock Pulse Generator
 compatible: "renesas,rza2m-cpg"
 
-include: renesas,rz-cpg.yml
+include: renesas,rz-cpg.yaml