drm/i915: fix guest virtual PCH detection on non-PCH systems

drm/i915: fix guest virtual PCH detection on non-PCH systems

Virtualized non-PCH systems such as Broxton or Geminilake should use
PCH_NONE to indicate no PCH rather than PCH_NOP. The latter is a
specific case to indicate a PCH system without south display.

Reported-by: Colin Xu <[email protected]>
Cc: Colin Xu <[email protected]>
Reviewed-by: Ville Syrjälä <[email protected]>
Tested-by: Colin Xu <[email protected]>
Reviewed-by: Colin Xu <[email protected]>
Signed-off-by: Jani Nikula <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]