drm/radeon/kms: add support for hardcoded edids in rom (v2)

Some servers hardcode an edid in rom so that they will
work properly with KVMs.  This is a port of the relevant
code from the ddx.

[airlied: reworked to validate edid at boot stage - and
remove special quirk, if there is a valid EDID in the BIOS rom
we'll just try and use it.]

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index d33c3e0..b420989 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -201,4 +201,7 @@
 
 #define EDID_PRODUCT_ID(e) ((e)->prod_code[0] | ((e)->prod_code[1] << 8))
 
+/* define the number of Extension EDID block */
+#define DRM_MAX_EDID_EXT_NUM 4
+
 #endif /* __DRM_EDID_H__ */