nv50,nvc0: add support for fine derivatives

The quadop-based method we currently use on all chipsets already
provides the fine version of the derivatives.

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

docs/relnotes/10.3.html

@@ -47,6 +47,7 @@ Note: some of the new features are only available with certain drivers.
 <li>GL_ARB_ES3_compatibility on nv50, nvc0, r600, radeonsi, softpipe, llvmpipe</li>
 <li>GL_ARB_clear_texture on i965</li>
 <li>GL_ARB_compressed_texture_pixel_storage on all drivers</li>
+<li>GL_ARB_derivative_control on nv50, nvc0</li>
 <li>GL_ARB_draw_indirect on nvc0, radeonsi</li>
 <li>GL_ARB_explicit_uniform_location (all drivers that support GLSL)</li>
 <li>GL_ARB_fragment_layer_viewport on nv50, nvc0, llvmpipe, r600</li>