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>

 diff -durN gcc-4.4.4.orig/gcc/config/sh/lib1funcs.asm gcc-4.4.4/gcc/config/sh/lib1funcs.asm

 --- gcc-4.4.4.orig/gcc/config/sh/lib1funcs.asm	2009-04-10 01:23:07.000000000 +0200

 +++ gcc-4.4.4/gcc/config/sh/lib1funcs.asm	2010-05-16 19:14:19.000000000 +0200

 @@ -30,6 +30,11 @@

  !! recoded in assembly by Toshiyasu Morita

  !! tm@netcom.com

 +#if defined(__ELF__) && defined(__linux__)

 +.section .note.GNU-stack,"",%progbits

 +.previous

 +#endif

 +

  /* SH2 optimizations for ___ashrsi3, ___ashlsi3, ___lshrsi3 and

     ELF local label prefixes by J"orn Rennecke

     amylaar@cygnus.com  */

 diff -durN gcc-4.4.4.orig/gcc/config/sh/linux-atomic.asm gcc-4.4.4/gcc/config/sh/linux-atomic.asm

 --- gcc-4.4.4.orig/gcc/config/sh/linux-atomic.asm	2009-04-10 01:23:07.000000000 +0200

 +++ gcc-4.4.4/gcc/config/sh/linux-atomic.asm	2010-05-16 19:14:19.000000000 +0200

 @@ -136,3 +136,6 @@

  ATOMIC_FETCH_AND_COMBOP(nand,and,not,4,l,mov)

  #endif /* ! __SH5__ */

 +

 +.section .note.GNU-stack,"",%progbits

 +.previous