drm/amd/display: Make dcn401_dsc_funcs static

The sparse tool complains as follows:

drivers/gpu/drm/amd/amdgpu/../display/dc/dsc/dcn401/dcn401_dsc.c:30:24: warning:
	symbol 'dcn401_dsc_funcs' was not declared. Should it be static?

This symbol is not used outside of dcn401_dsc.c, so marks it static.
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dsc/dcn401/dcn401_dsc.c

@@ -27,7 +27,7 @@ static void dsc401_disconnect(struct display_stream_compressor *dsc);
 static void dsc401_wait_disconnect_pending_clear(struct display_stream_compressor *dsc);
 static void dsc401_get_enc_caps(struct dsc_enc_caps *dsc_enc_caps, int pixel_clock_100Hz);
 
-const struct dsc_funcs dcn401_dsc_funcs = {
+static const struct dsc_funcs dcn401_dsc_funcs = {
 	.dsc_get_enc_caps = dsc401_get_enc_caps,
 	.dsc_read_state = dsc401_read_state,
 	.dsc_validate_stream = dsc401_validate_stream,