drm/i915: precendence bug in GT_PARITY_ERROR()

The | operation has higher precedence than "?:" so the macro always
returns GT_RENDER_L3_PARITY_ERROR_INTERRUPT_S1.

This regression has been introduce in "drm/i915: Add second slice l3
remapping".

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>