Add Linux v4l2 MFC support for ARM Exynos boards

Tested successfully with MFC5 (Exynos4) and MFC6 (Exynos5) on ODROID-U2, ODROID-U3 and ODROID-XU.

The codec queries MFC capabilities - MFC6 and above supports NV12, MFC5 supports NV12MT. When MFC5 is found, FIMC converter hardware found in Exynos4 is required. The PR contains V4L2 helper functions, MFC and FIMC code, and the dvdplayer codec.

Code was contributed by @owersun, @vamanea and @mihailescu2m.