drivers: video: sw_generator: fix video_sw_generator_enum_frmival()

Return an error on fie.index >= 1 as there is only one framerate entry
per pixelformat, this prevents an endless loop.

Signed-off-by: Josuah Demangeon <me@josuah.net>

Author: josuah

drivers/video/video_sw_generator.c

@@ -276,6 +276,10 @@ static int video_sw_generator_enum_frmival(const struct device *dev, struct vide
 	size_t idx;
 	int ret;
 
+	if (fie->index >= 1) {
+		return -ERANGE;
+	}
+
 	ret = video_format_caps_index(fmts, fie->format, &idx);
 	if (ret < 0) {
 		LOG_ERR("Unsupported pixel format or resolution");