Factor in clear values wherever required while updating destination
min/max.

References: HSDES#1604444184
Signed-off-by: NMichel Thierry <michel.thierry@intel.com>
Cc: mesa-dev@lists.freedesktop.org
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180510200708.18097-1-michel.thierry@intel.com
Cc: stable@vger.kernel.org