i965: Preserve EXEC_OBJECT_CAPTURE when growing the BO.
The original state buffer was marked with EXEC_OBJECT_CAPTURE. When growing it, we want to preserve that flag so we continue to capture it in GPU hang reports. Fixes: 2dfc119f "i965: Grow the batch/state buffers if we need space and can't flush." Reviewed-by:Ian Romanick <ian.d.romanick@intel.com>