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-4.4.0.orig/gcc/stmt.c gcc-4.4.0/gcc/stmt.c

 --- gcc-4.4.0.orig/gcc/stmt.c	2009-02-27 20:49:42.000000000 +0100

 +++ gcc-4.4.0/gcc/stmt.c	2009-05-27 21:38:21.000000000 +0200

 @@ -2376,7 +2376,11 @@

  	  use_cost_table

  	    = (TREE_CODE (orig_type) != ENUMERAL_TYPE

  	       && estimate_case_costs (case_list));

 -	  balance_case_nodes (&case_list, NULL);

 +	  /* When optimizing for size, we want a straight list to avoid

 +	     jumps as much as possible. This basically creates an if-else

 +	     chain.  */

 +	  if (!optimize_size)

 +	    balance_case_nodes (&case_list, NULL);

  	  emit_case_nodes (index, case_list, default_label, index_type);

  	  if (default_label)

  	    emit_jump (default_label);

 @@ -2942,6 +2946,7 @@

  	    {

  	      if (!node_has_low_bound (node, index_type))

  		{

 +		  if (!optimize_size) /* don't jl to the .default_label. */

  		  emit_cmp_and_jump_insns (index,

  					   convert_modes

  					   (mode, imode,