libdrm: Add initial implementation of libdrm for OpenFIMG

This is basically another front-end for Exynos DRM, but targeted more at
rendering devices, like FIMG-3DSE GPU present on Samsung S3C64xx,
S5PC100 and S5P6442 SoCs.

Heavily based on Freedreno libdrm code.

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>