radeon_hd: Fix DVI-I detection once and for all

* Reduced the logic down and only use it where
  possible.
* Remove the duplicate gpio pin check. While this
  is a determining factor... i'd rather get it
  right while detecting displays vs relying on
  connector order in the ASIC. This gpio pin check
  was also severely bugged (missing {}'s)
* Should fix #8913 and maybe others