lttng-modules: mark as broken on kernel version <3.18

On linux 3.14, we get errors like
error: 'struct snd_soc_codec' has no member named 'name'
__string( name, codec->CODEC_NAME_FIELD )
indicating that the module is incompatible with the linux API
in this kernel version.

See https://hydra.nixos.org/build/33102405/nixlog/1/raw

(cherry picked from commit a452b43ee5fd5e5321b5b5e6a233a118c4efeb07)
Signed-off-by: Domen Kožar <[e-mail]>

pkgs/os-specific/linux/lttng-modules/default.nix

···
     license = with licenses; [ lgpl21 gpl2 mit ];
     platforms = platforms.linux;
     maintainers = [ maintainers.bjornfor ];
-    broken = (kernel.features.grsecurity or false);
+    broken =
+      (builtins.compareVersions kernel.version "3.18" == -1) ||
+      (kernel.features.grsecurity or false);
   };
 
 }