drm/amd/display: make dcn32_split_stream_for_mpc_or_odm static

It's not used outside of dcn32_fpu.c.

Fixes: 20dad381 ("drm/amd/display: Add a helper to map ODM/MPC/Multi-Plane resources")
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dml/dcn32/dcn32_fpu.c

@@ -1372,7 +1372,7 @@ static struct pipe_ctx *dcn32_find_split_pipe(
 	return pipe;
 }
 
-bool dcn32_split_stream_for_mpc_or_odm(
+static bool dcn32_split_stream_for_mpc_or_odm(
 		const struct dc *dc,
 		struct resource_context *res_ctx,
 		struct pipe_ctx *pri_pipe,