nvc0: do not break the universe on GK110+

I removed that return 0 by mistake. Ooops.

Fixes: 6e23fd4 ("nvc0: allow to use compute support on GM200")
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>

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

@@ -647,6 +647,7 @@ nvc0_screen_init_compute(struct nvc0_screen *screen)
    case 0x120:
       if (debug_get_bool_option("NVF0_COMPUTE", false))
          return nve4_screen_compute_setup(screen, screen->base.pushbuf);
+      return 0;
    default:
       return -1;
    }