drm/i915: drop unnecessary clearing of pch dp transcoder timings

This has originally been added in

commit 8db9d77b
Author: Zhenyu Wang <zhenyuw@linux.intel.com>
Date:   Wed Apr 7 16:15:54 2010 +0800

    drm/i915: Support for Cougarpoint PCH display pipeline

probably to combat issues with hw state left behind by the BIOS. And
indeed, I've checked out that specific revision, and there is no DP
support yet. So the pch dp transcoder won't be correctly disabled, and
that's important since it requires a rether special disable dance:
Just writing 0 to TRANS_DP_CTL won't cut it, since we need to select
the NONE port when disabling, too.

And indeed, things seem to still work, so let's just remove this.

Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>