drm/nouveau: ltc/gf100-: fix cbc issues on certain boards

A mismatch between FB and LTC's idea of how big a large page is causes
issues such as black "holes" in rendering to occur on some boards
(those where LTC is configured for 64KiB large pages) when compression
is used.

Confirmed to fix at least the GK107 MBP.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>