videomodes: Add helper functions to parse video-mode env-var extra options

Add 2 helper functions to get strings, respectively integers from the options
value returned by video_get_video_mode() / video_get_ctfb_res_modes().

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Anatolij Gustschin <agust@denx.de>
diff --git a/drivers/video/videomodes.h b/drivers/video/videomodes.h
index 02419cd..047b8a9 100644
--- a/drivers/video/videomodes.h
+++ b/drivers/video/videomodes.h
@@ -84,3 +84,8 @@
 			      const struct ctfb_res_modes **mode_ret,
 			      unsigned int *depth_ret,
 			      const char **options);
+
+void video_get_option_string(const char *options, const char *name,
+			     char *dest, int dest_len, const char *def);
+
+int video_get_option_int(const char *options, const char *name, int def);