drm/i915: don't write 0 to DIP control at HDMI init

At this time, the HDMI port is enabled, and the DIP control register
specification says we need to disable the port *before* disabling the
DIPs. Also, while doing this we risk telling the HW to send the AVI
DIPs once (not every VSync), which really seems to confuse the HW and
trigger bugs where the DIPs are not sent.

This code was here just to set the DIP register to a 'known state'
before using it, but since now the set_infoframes functions already
set the control registers to a known state, this code can go away.

Also, the previous code disables *all* the DIP registers for *each*
HDMI port, so we end disabling each DIP register more than once.

This patch solves a problem I can reproduce on my IVB machine. When I
boot it with just a single HDMI monitor, the AVI InfoFrames are not
sent. With this patch, the InfoFrames are sent. Previously, I wrote a
patch to 'touch the DIP registers after we enable the HDMI port' to
solve this same problem, but that patch doesn't seem to be needed
anymore after this patch.

All this patch does is revert a chunk of the following commit:

    commit 64a8fc01
    Author: Jesse Barnes <jbarnes@virtuousgeek.org>
    Date:   Thu Sep 22 11:16:00 2011 +0530

        drm/i915: fix ILK+ infoframe support

So bugs that can be bisected to that commit may be fixed now.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=43256


Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>