drm/amd/display: change to enc314_stream_encoder_dp_blank static

enc314_stream_encoder_dp_blank is only used in dcn314_dio_stream_encoder.c now,
change it to static.

Fixes: c55bf690 ("drm/amd/display: Add explicit FIFO disable for DP blank")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn314/dcn314_dio_stream_encoder.c

@@ -262,7 +262,7 @@ static bool is_two_pixels_per_containter(const struct dc_crtc_timing *timing)
 	return two_pix;
 }
 
-void enc314_stream_encoder_dp_blank(
+static void enc314_stream_encoder_dp_blank(
 	struct dc_link *link,
 	struct stream_encoder *enc)
 {