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 -u binutils-2.18-orig/configure binutils-2.18/configure

 --- binutils-2.18-orig/configure	2007-08-06 16:29:40.000000000 -0400

 +++ binutils-2.18/configure	2007-09-27 22:41:51.000000000 -0400

 @@ -6125,10 +6125,10 @@

    *" texinfo "*) MAKEINFO='$$r/$(BUILD_SUBDIR)/texinfo/makeinfo/makeinfo' ;;

    *)

 -    # For an installed makeinfo, we require it to be from texinfo 4.4 or

 +    # For an installed makeinfo, we require it to be from texinfo 4.6 or

      # higher, else we use the "missing" dummy.

      if ${MAKEINFO} --version \

 -       | egrep 'texinfo[^0-9]*([1-3][0-9]|4\.[4-9]|[5-9])' >/dev/null 2>&1; then

 +       | egrep 'texinfo[^0-9]*(4\.([6-9]|[1-9][0-9])|[5-9]|[1-9][0-9])' >/dev/null 2>&1; then

        :

      else

        MAKEINFO="$MISSING makeinfo"