arch/powerpc: add powerpc64le support

Technically, I don't forbid powerpcle support either, but I'm not sure that
there is any library/compiler support for that at the moment (though the hw
technically makes it possible).

powerpc64le needs glibc 2.19 and gcc 4.9. I haven't looked into the support
tools, but at least gdb 7.5 is too old (7.7.1 definitely has support).

Also make powerpc64 non-experimental. It's practically old at this point.

Signed-off-by: Cody P Schafer <dev@codyps.com>
[yann.morin.1998@free.fr: use ${target_endian_le} and ${target_bits_64}]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Message-Id: <64bfbbced9dd8f62e0d6.1399801945@gun>
Patchwork-Id: 347775

diff -durN gcc-4.2.3.orig/gcc/config/arm/linux-eabi.h gcc-4.2.3/gcc/config/arm/linux-eabi.h

--- gcc-4.2.3.orig/gcc/config/arm/linux-eabi.h	2007-09-01 17:28:30.000000000 +0200

+++ gcc-4.2.3/gcc/config/arm/linux-eabi.h	2008-05-25 23:47:36.000000000 +0200

@@ -47,7 +47,8 @@

 #define SUBTARGET_CPU_DEFAULT TARGET_CPU_arm10tdmi

 #undef SUBTARGET_EXTRA_LINK_SPEC

-#define SUBTARGET_EXTRA_LINK_SPEC " -m armelf_linux_eabi"

+#define SUBTARGET_EXTRA_LINK_SPEC	\

+	" %{mlittle-endian:-m armelf_linux_eabi} %{mbig-endian:-m armelfb_linux_eabi}"

 /* Use ld-linux.so.3 so that it will be possible to run "classic"

    GNU/Linux binaries on an EABI system.  */