Revert "drm/i915: Nuke pipe A quirk on i830M"

830 really does want the pipe A quirk. The planes and ports don't
react to any register writes unless the pipe currently attached
to them is running, so it's impossible to move them to the other
pipe unless both pipes are running.

Also it's documented that the DPLL must be enabled on both pipes
whenever it's needed.

This reverts commit ac6696d3236bd61503f89a1a99680fd7894d5d53.

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>