drm/i915: Gen2 FBC1 CFB pitch wants 32B units

On gen2 the compressed frame buffer pitch is specified in 32B units
rather than the 64B units used on gen3+.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>