drm/i915: Don't clobber CHICKEN_PIPESL_1 on BDW

Misplaced parens cause us to totally clobber the CHICKEN_PIPESL_1
registers with 0xffffffff. Move the parens to the correct place
to avoid this.

In particular this caused bit 30 of said registers to be set, which
caused the sprite CSC to produce incorrect results.

Cc: stable@vger.kernel.org
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=72220


Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>