drm/i915: simplify DP/DDI port width macros

drm/i915: simplify DP/DDI port width macros

If we ever leak a non-DP compliant port width through here, we have a
pretty serious issue. So just rip out all these WARNs - if we need
them it's probably better to have them at a central place where we
compute the dp lane count.

Also use the new DDI width macro for FDI mode.

Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
[danvet: fixup the embarrassing s/intel_dp->DP/temp/ mistake Paulo
spotted.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>