intel/blorp_blit: Fix max blit size for gen6

Fixes ES3-CTS.gtf.GL3Tests.framebuffer_blit.framebuffer_blit_functionality_stencil_blit

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
diff --git a/src/intel/blorp/blorp_blit.c b/src/intel/blorp/blorp_blit.c
index 8abe3a8..1cbd940 100644
--- a/src/intel/blorp/blorp_blit.c
+++ b/src/intel/blorp/blorp_blit.c
@@ -1522,10 +1522,11 @@
 get_max_surface_size(const struct gen_device_info *devinfo,
                      const struct blorp_params *params)
 {
+   const unsigned max = devinfo->gen >= 7 ? 16384 : 8192;
    if (split_blorp_blit_debug && can_shrink_surfaces(params))
-      return 16384 >> 4; /* A smaller restriction when debug is enabled */
+      return max >> 4; /* A smaller restriction when debug is enabled */
    else
-      return 16384;
+      return max;
 }
 
 struct blt_axis {