scripts: dts: Consistently open text files with utf-8.

Zephyr codebase standardizes in UTF-8 as file encoding. To
accommodate this, we explicitly pass encoding="utf-8" to Python's
open() function, to be independent of any locale setting of a
particular system (e.g., CI/build systems oftentimes have "C",
i.e. ASCII-only, locale). In a few places, we lacked this parameter,
so add it consistently.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>

scripts/dts/edtlib.py

@@ -1029,7 +1029,7 @@ def _binding_compat(binding_path):
     # Uses a regex to avoid having to parse the bindings, which is slow when
     # done for all bindings.
 
-    with open(binding_path) as binding:
+    with open(binding_path, encoding="utf-8") as binding:
         for line in binding:
             match = re.match(r'\s+constraint:\s*"([^"]*)"', line)
             if match: