drm/i915: Undo the PIPEA quirk for i845

The PIPEA quirk is specifically for the issue with the PIPEB PLL on
830gm being slaved to the PIPEA PLL, and so to use PIPEB requires PIPEA
running. i845 doesn't even have the second PLL or pipe, and enabling
the quirk results in a blank DVO LVDS.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>