drm/udl: Refactor edid retrieving in UDL driver (v2)

Now drm/udl driver uses drm_do_get_edid() function to retrieve and
validate all blocks of EDID data. Old approach had insufficient
validation routine and had problems with retrieving of extra blocks

Signed-off-by: Robert Tarasov <tutankhamen@chromium.org>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
[airlied: Fix spelling mistakes]
Link: https://patchwork.freedesktop.org/patch/msgid/20190314225339.162386-1-tutankhamen@chromium.org