nvc0: enable GL_NV_shader_atomic_float on pre-Maxwell

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>

docs/relnotes/19.0.0.html

@@ -46,6 +46,7 @@ TBD.
 <li>GL_EXT_render_snorm on gallium drivers (ES extension).</li>
 <li>GL_EXT_texture_view on drivers supporting texture views (ES extension).</li>
 <li>GL_OES_texture_view on drivers supporting texture views (ES extension).</li>
+<li>GL_NV_shader_atomic_float on nvc0 (Fermi/Kepler only).</li>
 </ul>
 
 <h2>Bug fixes</h2>

src/gallium/drivers/nouveau/nvc0/nvc0_screen.c

@@ -275,6 +275,8 @@ nvc0_screen_get_param(struct pipe_screen *pscreen, enum pipe_cap param)
    case PIPE_CAP_TGSI_BALLOT:
    case PIPE_CAP_BINDLESS_TEXTURE:
       return class_3d >= NVE4_3D_CLASS;
+   case PIPE_CAP_TGSI_ATOMFADD:
+      return class_3d < GM107_3D_CLASS; /* needs additional lowering */
    case PIPE_CAP_POLYGON_MODE_FILL_RECTANGLE:
    case PIPE_CAP_TGSI_VS_LAYER_VIEWPORT:
    case PIPE_CAP_TGSI_TES_LAYER_VIEWPORT: