decklink: Support 2K DCI video modes
This extends the video modes supported by the decklink plugin to include 2K DCI (2048x1080) modes.
For this to work, it was necessary to upgrade the Decklink SDK to version 10.11.4, since the previous version (10.8) did not fully support 2K DCI modes (support was output only).
Note: The current latest version of the Decklink SDK is 11.5, however the gstreamer decklink plugin is not compatible with API changes introduced in version 11 of the SDK. Therefore I have opted to upgrade to the latest 10.x version instead.