Add support for Exynos HDMI

This pull request adds support for Exynos based chips. Currently it has been tested on the HTPC boards provided by Hardkernel http://www.hardkernel.com/main/main.php but it most likely works with other devices too.

The driver is quite simple, the device provides raw access to the CEC bus via the /dev/CEC device node. One can write raw CEC frames to /dev/CEC and also read/poll the it for incoming data. There is no ACK mechanism but a write will fail if a non-existant logical address is used.