drm/i915: rip out the pipe A quirk for i855gm

This seems to be the root-cause that breaks resume on my i855gm when I
apply the "drm/i915: fixup the plane->pipe fixup code" patch. And that
code doesn't even run on my machine, so it's pure timing changes
causing the regression.

Furthermore resume has been constantly switching between working and
broken on this machine ever since kms support has been merged,
seemingly with no related change as a root cause. And always with the
same symptoms of the backlight lighting up, but the lvds panel only
displaying black.

Also, of both i855gm variants only one is in the table. And in the
past we've only ever removed entries from this quirk table because it
breaks things.

So let's just remove it - in case there's indeed a bios out there
relying on a running pipe A, we can add back in a more precise quirk
entry, like all the others (save for i830/i845).

Tested-by: Chris Wilson <chris@chris-wilson.co.uk> #855gm
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>