scripts: Loader change

CSafeLoader used instead of yaml.safe_load and SafeLoader.
C implementation is faster.

Signed-off-by: Lukasz Mrugala <lukaszx.mrugala@intel.com>
diff --git a/scripts/list_boards.py b/scripts/list_boards.py
index b768dd6..6b810d0 100755
--- a/scripts/list_boards.py
+++ b/scripts/list_boards.py
@@ -15,9 +15,14 @@
 import list_hardware
 from list_hardware import unique_paths
 
+try:
+    from yaml import CSafeLoader as SafeLoader
+except ImportError:
+    from yaml import SafeLoader
+
 BOARD_SCHEMA_PATH = str(Path(__file__).parent / 'schemas' / 'board-schema.yml')
 with open(BOARD_SCHEMA_PATH, 'r') as f:
-    board_schema = yaml.safe_load(f.read())
+    board_schema = yaml.load(f.read(), Loader=SafeLoader)
 
 BOARD_YML = 'board.yml'
 
@@ -178,7 +183,7 @@
     boards = []
     if board_yml.is_file():
         with board_yml.open('r') as f:
-            b = yaml.safe_load(f.read())
+            b = yaml.load(f.read(), Loader=SafeLoader)
 
         try:
             pykwalify.core.Core(source_data=b, schema_data=board_schema).validate()