mips linux: Adding a patch to fix an ext3 bug in 3.5 and 3.6

I made it apply to all Mips, although the bug works only for n32 and o32 ABIs.
We don't support any n64 by now.

pkgs/os-specific/linux/kernel/mips-ext3-n32.patch

···
+Dirty patch that makes ext3 work again on 3.5 and 3.6 kernels,
+on mips n32.
+
+http://www.linux-mips.org/archives/linux-mips/2012-11/msg00030.html
+
+diff --git a/fs/ext3/dir.c b/fs/ext3/dir.c
+index 92490e9..bf63d7b 100644
+--- a/fs/ext3/dir.c
++++ b/fs/ext3/dir.c
+@@ -228,6 +228,7 @@ out:
+ 
+ static inline int is_32bit_api(void)
+ {
++	return 1;
+ #ifdef CONFIG_COMPAT
+ 	return is_compat_task();
+ #else

pkgs/os-specific/linux/kernel/patches.nix

···
       patch = ./mips-fpu-sigill.patch;
     };
 
+  mips_ext3_n32 =
+    { name = "mips-ext3-n32";
+      patch = ./mips-ext3-n32.patch;
+    };
+
   guruplug_defconfig =
     { # Default configuration for the GuruPlug.  From
       # <http://www.openplug.org/plugwiki/images/c/c6/Guruplug-patchset-2.6.33.2.tar.bz2>.

pkgs/top-level/all-packages.nix

···
       ] ++ lib.optionals (platform.kernelArch == "mips")
       [ kernelPatches.mips_fpureg_emu
         kernelPatches.mips_fpu_sigill
+        kernelPatches.mips_ext3_n32
       ];
   };
 
···
       ] ++ lib.optionals (platform.kernelArch == "mips")
       [ kernelPatches.mips_fpureg_emu
         kernelPatches.mips_fpu_sigill
+        kernelPatches.mips_ext3_n32
       ];
   };