docs: update with ARB_texture_cube_map_array support

just mention softpipe is done, r600g will come soon.

Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/docs/relnotes-9.1.html b/docs/relnotes-9.1.html
index 5bf9d8c..97247fb 100644
--- a/docs/relnotes-9.1.html
+++ b/docs/relnotes-9.1.html
@@ -45,6 +45,7 @@
 
 <ul>
 <li>GL_ARB_map_buffer_alignment</li>
+<li>GL_ARB_texture_cube_map_array</li>
 </ul>