toolchain-external: update AArch64 Linaro toolchains

Add the AArch64 Linaro toolchains 2013.02 and 2013.03, remove 2012.11
and 2012.12.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>