Starting with Haswell, DDI ports can work in FDI mode to support
connectivity with the outputs located on the PCH.

This commit adds support for such connections in the intel_ddi module, and
provides Haswell-specific functionality to make it work.

v2: simplify the commit as per Daniel Vetter suggestion.
Signed-off-by: NEugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

DDI is introduced starting with Haswell GPU generation. So to simplify its
management in the future, we also add intel_ddi.c to hold all the
DDI-related items.

Buffer translations for DDI links must be initialized prior to enablement.
For FDI and DP, first 9 pairs of values are used to select the connection
parameters. HDMI uses the last pair of values and ignores the first 9
pairs. So we program HDMI values in both cases, which allows HDMI to work
over both FDI and DP-friendly buffers.
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NEugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>