drm/i915: preserve dispaly init order on ByT

This patch changes HDMI port registration order for the BayTrail platform.

The story is that in kernel version 3.11 i915 supported only one HDMI port -
the HDMIB port. So this port ended up being HDMI-1 in user-space.

But commit '6f6005a5 drm/i915: expose HDMI connectors on port C on BYT'
introduced HDMIC port support. And added HDMIC  registration prior to HDMIB,
so HDMIB became HDMI-2 and HDMIC became HDMI-1.

Well, this is fine as far as the kernel is concerned. i915 does not give any
guarantees to the numbering, and has never given them.

However, this breaks wayland setup in Tizen IVI. We have only one single HDMI
port on our hardware, and it is connected to HDMIB. Our configuration relies on
the fact that it is HDMI-1.

Well, certainly this is user-space problem which was exposed with Jesse's
patch. However, there is a reason why we have to do this assumption - we use
touchscreen monitors and we have to associate event devices with the monitors,
and this is not easy to do dynamically, so we just have a static setup.

Anyway, while the user-space setup will have to be fixed regardless, let's
chane the HDMI port registration order so that HDMIB stays HDMI-1, just like it
was in 3.11. Simply because there is no strong reason for changing the order in
the kernel, and it'll help setups like ours in sense that we'll have more time
for fixing the issue properly.

Also amend the commentary which looks a bit out-of-date.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
[danvet: Drop the commment, SDVOC is gone and we have a proper HDMIC
define now.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>