cogl: return correct enum type

cogl_pipeline_get_front_face_winding() is supposed to return a CoglWinding. It
takes a CoglPipeline as argument and does the following input validation:

g_return_val_if_fail (cogl_is_pipeline (pipeline),
                      COGL_PIPELINE_CULL_FACE_MODE_NONE);

The returned COGL_PIPELINE_CULL_FACE_MODE_NONE is not a winding.

The function was added with this check 8 years ago in
5369b3c601fc537db6712c27a5453fa11236c66b

I do not see any of the two options in the CoglWinding as particularly good
choice for a return value on bad input, but let's go with
COGL_WINDING_CLOCKWISE as that is equivalent with the behavior for all
these years.

Definitions of the two enums:

typedef enum
{
  COGL_WINDING_CLOCKWISE,
  COGL_WINDING_COUNTER_CLOCKWISE
} CoglWinding;

typedef enum
{
  COGL_PIPELINE_CULL_FACE_MODE_NONE,
  COGL_PIPELINE_CULL_FACE_MODE_FRONT,
  COGL_PIPELINE_CULL_FACE_MODE_BACK,
  COGL_PIPELINE_CULL_FACE_MODE_BOTH
} CoglPipelineCullFaceMode;

https://gitlab.gnome.org/GNOME/mutter/merge_requests/934

cogl/cogl/cogl-pipeline-state.c

@@ -973,7 +973,7 @@ cogl_pipeline_get_front_face_winding (CoglPipeline *pipeline)
   CoglPipeline *authority;
 
   g_return_val_if_fail (cogl_is_pipeline (pipeline),
-                        COGL_PIPELINE_CULL_FACE_MODE_NONE);
+                        COGL_WINDING_CLOCKWISE);
 
   authority = _cogl_pipeline_get_authority (pipeline, state);