drm/i915: FDI link training broken on Ironlake by Ivybridge integration

Commit 357555c0 split out IVB-specific
register definitions for FDI link training, but a piece of that commit
stopped executing some critical code on Ironlake systems while leaving
it running on Sandybridge.

Turn that code back on both Ironlake and Sandybridge

Signed-off-by: Keith Packard <keithp@keithp.com>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>