Documentation/changes: Raise minimum supported binutils version to 2.23

The currently minimum-supported binutils version 2.21 has the problem of
promoting symbols which are defined outside of a section into absolute.
According to Arvind:

  binutils-2.21 and -2.22. An x86-64 defconfig will fail with
          Invalid absolute R_X86_64_32S relocation: _etext
  and after fixing that one, with
          Invalid absolute R_X86_64_32S relocation: __end_of_kernel_reserve

Those two versions of binutils have a bug when it comes to handling
symbols defined outside of a section and binutils 2.23 has the proper
fix, see: https://sourceware.org/legacy-ml/binutils/2012-06/msg00155.html

Therefore, up to the fixed version directly, skipping the broken ones.

Currently shipping distros already have the fixed binutils version so
there should be no breakage resulting from this.

For more details about the whole thing, see the thread in Link.

Signed-off-by: Borislav Petkov <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Acked-by: Kees Cook <[email protected]>
Acked-by: Jason A. Donenfeld <[email protected]>
Acked-by: Nick Desaulniers <[email protected]>
Acked-by: Ingo Molnar <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>

Documentation/process/changes.rst

@@ -31,7 +31,7 @@ you probably needn't concern yourself with pcmciautils.
 ====================== ===============  ========================================
 GNU C                  4.6              gcc --version
 GNU make               3.81             make --version
-binutils               2.21             ld -v
+binutils               2.23             ld -v
 flex                   2.5.35           flex --version
 bison                  2.0              bison --version
 util-linux             2.10o            fdformat --version
@@ -76,7 +76,7 @@ You will need GNU make 3.81 or later to build the kernel.
 Binutils
 --------
 
-Binutils 2.21 or newer is needed to build the kernel.
+Binutils 2.23 or newer is needed to build the kernel.
 
 pkg-config
 ----------