lib/edid.c: Differentiate between absent and non-conformant EDID

Change-Id: Id90aa210ff72092c4ab638a7bafb82bd11889bdc
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/19502
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/include/edid.h

@@ -91,6 +91,12 @@ struct edid {
 	int hdmi_monitor_detected;
 };
 
+enum edid_status {
+	EDID_CONFORMANT,
+	EDID_NOT_CONFORMANT,
+	EDID_ABSENT,
+};
+
 /* Defined in src/lib/edid.c */
 int decode_edid(unsigned char *edid, int size, struct edid *out);
 void edid_set_framebuffer_bits_per_pixel(struct edid *edid, int fb_bpp,