colibri-imx6ull: remove tezi support for the 256MB version

The tezi image contains IDs for all the supported device types.
remove ID for the 256MB version that doesn't have enough space
for the tezi image. SD card image will still work correctly.

Change-Id: Ie0d5103b0c538f1a4a0150b73cc35248173cd3eb
Reviewed-by: Mikko Gronoff <mikko.gronoff@qt.io>