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

# MIPS specific config options

choice

    bool

    prompt "ABI"

config ARCH_mips_o32

    bool

    prompt "o32"

    depends on ARCH_32

    help

      This is the -mabi=32 gcc option.

config ARCH_mips_n32

    bool

    prompt "n32"

    depends on ARCH_64

    help

      This is the -mabi=n32 gcc option.

config ARCH_mips_n64

    bool

    prompt "n64"

    depends on ARCH_64

    help

      This is the -mabi=64 gcc option.

# Not supported on Linux:

# o64   : seems related to *BSD

# eabi  : seems related to bare-metal

endchoice

config ARCH_mips_ABI

    string

    default "32"    if ARCH_mips_o32

    default "n32"   if ARCH_mips_n32

    default "64"    if ARCH_mips_n64