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>

 --- gcc-4.3.2.orig/gcc/config/arm/linux-eabi.h	2009-09-08 23:46:44.000000000 +0200

 +++ gcc-4.3.2/gcc/config/arm/linux-eabi.h	2009-09-08 23:46:51.000000000 +0200

 @@ -44,7 +44,7 @@

     The ARM10TDMI core is the default for armv5t, so set

     SUBTARGET_CPU_DEFAULT to achieve this.  */

  #undef  SUBTARGET_CPU_DEFAULT

 -#define SUBTARGET_CPU_DEFAULT TARGET_CPU_arm10tdmi

 +#define SUBTARGET_CPU_DEFAULT TARGET_CPU_arm9tdmi

  /* TARGET_BIG_ENDIAN_DEFAULT is set in

     config.gcc for big endian configurations.  */