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

 CT_EXPERIMENTAL=y

 CT_LOCAL_TARBALLS_DIR="${HOME}/src"

 CT_SAVE_TARBALLS=y

 CT_LOG_EXTRA=y

 CT_ARCH_CPU="cortex-m3"

 CT_ARCH_TUNE="cortex-m3"

 CT_ARCH_FLOAT_SW=y

 CT_ARCH_arm=y

 # CT_ARCH_USE_MMU is not set

 CT_ARCH_ARM_MODE_THUMB=y

 CT_TARGET_VENDOR="bare_newlib_cortex_m3_nommu"

 CT_ARCH_BINFMT_FLAT=y

 CT_BINUTILS_V_2_19_1a=y

 CT_CC_V_4_4_1=y

 CT_CC_LANG_CXX=y

 CT_LIBC_NEWLIB_V_1_18_0=y

 CT_GMP_V_4_3_2=y

 CT_MPFR_V_2_4_2=y

 CT_PPL_V_0_10_2=y

 CT_CLOOG_V_0_15_9=y