drm/i915: ns2501 is on DVOB

On Fujitsu-Siememens S6010 the ns2501 chip is hooked up to DVOB instead
of DVOC.

FIXME: Maybe need to dig out the correct DVO port from VBT

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Tested-by: Thomas Richter <richter@rus.uni-stuttgart.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>