toolchain-external: bump Linaro AArch64 to 2015.11-2

Runtime tested with Qemu 2.3.1 using qemu_aarch64_virt_defconfig.

Signed-off-by: Romain Naour <romain.naour@gmail.com>
[Thomas: only add the symlink with the old 2014.09 Linaro toolchain,
for the newer ones, it is no longer needed. This has been runtime
tested in Qemu.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>