kernel/linux: fix using custom location

Currently, extract and patch are skipped as thus:
- using a custom directory of pre-installed headers
- a correctly named directory already exists

Otherwise, extract and patch are done.

The current second condition is wrong, because it allows the following
sequence to happen:
- a non-custom kernel is used
- a previous build only partially extracted the non-custom sources
- that p[revious build broke during extraction (eg. incomplete tarball...)
- a subsequent build will find a properly named directory, and will
thus skip extract and patch, which is wrong

Fix that by following the conditions in this table:

Type | Extract | Patch
----------------------+---------+-------
Pre-installed headers | N | N
custom directory | N | N
custom tarball | Y | N
mainstream tarball | Y | Y

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: David Holsgrove <david.holsgrove@xilinx.com>

 2011-02-28  Aurelien Jarno  <aurelien@aurel32.net>

 	* sysdeps/unix/sysv/linux/mips/bits/statfs.h (struct statfs,

 	struct statfs64): Add f_flags field.

 diff --git glibc-2.13/glibc-ports-2.13/sysdeps/unix/sysv/linux/alpha/bits/statfs.h glibc-2.13/glibc-ports-2.13/sysdeps/unix/sysv/linux/alpha/bits/statfs.h

 index d838e6b..157591d 100644

 --- glibc-2.13/glibc-ports-2.13/sysdeps/unix/sysv/linux/alpha/bits/statfs.h

 +++ glibc-2.13/glibc-ports-2.13/sysdeps/unix/sysv/linux/alpha/bits/statfs.h

 @@ -42,7 +42,8 @@ struct statfs

      __fsid_t f_fsid;

      int f_namelen;

      int f_frsize;

 -    int f_spare[5];

 +    int f_flags;

 +    int f_spare[4];

    };

  #ifdef __USE_LARGEFILE64

 @@ -58,7 +59,8 @@ struct statfs64

      __fsid_t f_fsid;

      int f_namelen;

      int f_frsize;

 -    int f_spare[5];

 +    int f_flags;

 +    int f_spare[4];

    };

  #endif