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>

 From 83a09cd5c9ed9afd87a7d1d17319c2fd2203ad0f Mon Sep 17 00:00:00 2001

 From: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

 Date: Thu, 21 Jan 2010 10:36:13 +0100

 Subject: [PATCH 04/15] rpc: fix typo in version mismatch msg

 Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

 ---

  libc/inet/rpc/rpc_prot.c |    2 +-

  1 files changed, 1 insertions(+), 1 deletions(-)

 diff --git a/libc/inet/rpc/rpc_prot.c b/libc/inet/rpc/rpc_prot.c

 index 74658e6..229f988 100644

 --- a/libc/inet/rpc/rpc_prot.c

 +++ b/libc/inet/rpc/rpc_prot.c

 @@ -229,7 +229,7 @@ rejected (enum reject_stat rjct_stat,

  {

    switch (rjct_stat)

      {

 -    case RPC_VERSMISMATCH:

 +    case RPC_MISMATCH:

        error->re_status = RPC_VERSMISMATCH;

        return;

      case AUTH_ERROR:

 -- 

 1.6.6.1