imx6qdl-santaro.dtsi: fix typo in ddc-i2c-bus property name

In bug report (https://secogroup.atlassian.net/browse/YT-70) dedicated to HDMI testing, we articulated that with "kuk" kernel, an HDMI resolution is set to 640x480 only when we specify "mode=preferred" in weston.ini. But before experimenting with "kuk" kernel, we decided to investigate why the problem cannot be reproduced on the "guf" kernel.

And during our experiments, we found a typo in device tree for "guf" kernel. This MR fixes this issue.