mesa: enable texture floats only for drivers

To be on more safe side. This shouldn't matter theoretically as nothing in core
Mesa depends on them.

pkgs/development/libraries/mesa/default.nix

@@ -5,8 +5,9 @@
 , libelf, libvdpau, python2
 , grsecEnabled ? false
 , enableRadv ? false
-# Texture floats are patented, see docs/patents.txt, but Debian enables them.
-, enableTextureFloats ? true
+# Texture floats are patented, see docs/patents.txt, so we don't enable them for full Mesa.
+# It's overridden for mesa_drivers.
+, enableTextureFloats ? false
 , galliumDrivers ? null
 , driDrivers ? null
 , vulkanDrivers ? null

pkgs/top-level/all-packages.nix

@@ -8991,6 +8991,7 @@ with pkgs;
   mesa_drivers = mesaDarwinOr (
     let mo = mesa_noglu.override {
       grsecEnabled = config.grsecurity or false;
+      enableTextureFloats = true;
     };
     in mo.drivers
   );