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>

 2007-03-13  Mike Frysinger  <vapier@gentoo.org>

 	* sysdeps/unix/sysv/linux/sh/sys/procfs.h: Copy Linux's asm-sh/elf.h types.

 --- glibc-2_9/sysdeps/unix/sysv/linux/sh/sys/procfs.h

 +++ glibc-2_9/sysdeps/unix/sysv/linux/sh/sys/procfs.h

 @@ -29,10 +29,19 @@

  #include <sys/types.h>

  #include <sys/ucontext.h>

  #include <sys/user.h>

 -#include <asm/elf.h>

  __BEGIN_DECLS

 +/*

 + * ELF register definitions...

 + */

 +typedef unsigned long elf_greg_t;

 +

 +#define ELF_NGREG (sizeof (struct pt_regs) / sizeof(elf_greg_t))

 +typedef elf_greg_t elf_gregset_t[ELF_NGREG];

 +

 +typedef struct user_fpu_struct elf_fpregset_t;

 +

  struct elf_siginfo

    {

      int si_signo;			/* Signal number.  */