drm/amd/display: fix a divide by zero error

[Why&How]

Incorrect variable was being checked for zero condition.
Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Acked-by: Jasdeep Dhillon <jdhillon@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource_helpers.c

@@ -278,7 +278,7 @@ void dcn32_determine_det_override(struct dc *dc,
 		}
 	}
 
-	if (context->stream_count > 0) {
+	if (stream_count > 0) {
 		stream_segments = 18 / stream_count;
 		for (i = 0; i < context->stream_count; i++) {
 			if (context->streams[i]->mall_stream_config.type == SUBVP_PHANTOM)