drm/i915: Get rid of the gm45 HPD live state nonsense

The idea that ctg uses different HPD live state bits is
total nonsense, at least on my machine (Dell Latitude
E5400).

The only reason DP-B even works on my ctg is that DP-D
live state is stuck high, even though there is no physical
DP-D port. So when the detect checks DP-B live state it
sees the stuck live state of DP-D instead. If I hack
the driver to not register DP-D at all, and thus we never
enabe DP-D HPD, DP-B stops working as well.

Just to put some conclusive evidence into this mess,
here are the actual hotplug register values for each port:
 Everything disconnected:
                    PORT_HOTPLUG_EN (0x00061110): 0x00000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x00000000
                    PORT_HOTPLUG_EN (0x00061110): 0x08000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x08000000
                    PORT_HOTPLUG_EN (0x00061110): 0x10000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x00000000
                    PORT_HOTPLUG_EN (0x00061110): 0x20000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x00000000
 Only port B connected:
                    PORT_HOTPLUG_EN (0x00061110): 0x00000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x00000000
                    PORT_HOTPLUG_EN (0x00061110): 0x08000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x08000000
                    PORT_HOTPLUG_EN (0x00061110): 0x10000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x00000000
                    PORT_HOTPLUG_EN (0x00061110): 0x20000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x20000000
 Only port C connected:
                    PORT_HOTPLUG_EN (0x00061110): 0x00000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x00000000
                    PORT_HOTPLUG_EN (0x00061110): 0x08000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x08000000
                    PORT_HOTPLUG_EN (0x00061110): 0x10000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x10000000
                    PORT_HOTPLUG_EN (0x00061110): 0x20000000
                  PORT_HOTPLUG_STAT (0x00061114): 0x00000000

So the enable bit and live state bit always match 1:1.

Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230302161013.29213-4-ville.syrjala@linux.intel.com