enable relaxed fencing on inteldrm

[Jonathan Gray]

This may give a speedup in some cases as we will allocate less
memory up front.  It needs to be tested across a diverse set of
hardware for regressions however.

Requires the gtt changes kettenis recently committed.

Index: i915_dma.c
===================================================================
RCS file: /cvs/src/sys/dev/pci/drm/i915/i915_dma.c,v
retrieving revision 1.11
diff -u -p -r1.11 i915_dma.c
--- i915_dma.c  19 Nov 2013 19:14:09 -0000      1.11
+++ i915_dma.c  20 Nov 2013 02:10:31 -0000
@@ -105,11 +105,7 @@ i915_getparam(struct drm_device *dev, vo
                value = intel_ring_initialized(&dev_priv->ring[BCS]);
                break;
        case I915_PARAM_HAS_RELAXED_FENCING:
-#ifdef notyet
                value = 1;
-#else
-               return -EINVAL;
-#endif
                break;
        case I915_PARAM_HAS_COHERENT_RINGS:
                value = 1;