drm/i915: Remove mention of Haswell in DDI code

We are trying to have more platform-orthogonal pieces of code. The DDI
code shouldn't mention Haswell.

v2: Fix the email address

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>