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>

 Original patch from: ../4.3.2/170-libiberty-pic.patch

 -= BEGIN original header =-

 Original patch from gentoo: gentoo/src/patchsets/gcc/4.3.1/gentoo/51_all_gcc-3.4-libiberty-pic.patch

 -= END original header =-

 diff -durN gcc-4.3.3.orig/libiberty/Makefile.in gcc-4.3.3/libiberty/Makefile.in

 --- gcc-4.3.3.orig/libiberty/Makefile.in	2007-07-25 08:26:45.000000000 +0200

 +++ gcc-4.3.3/libiberty/Makefile.in	2009-01-27 22:19:30.000000000 +0100

 @@ -225,6 +225,7 @@

  	  $(AR) $(AR_FLAGS) $(TARGETLIB) \

  	    $(REQUIRED_OFILES) $(EXTRA_OFILES) $(LIBOBJS); \

  	  $(RANLIB) $(TARGETLIB); \

 +	  cp $(TARGETLIB) ../ ; \

  	  cd ..; \

  	else true; fi