linux-gen: time: fix ARM compile for GCC 4.8
linux-gen: time: fix ARM compile for GCC 4.8

Use __aarch64__ instead of __ARM_ARCH, since it's backwards
compatible between GCC versions.

Fixes bug https://bugs.linaro.org/show_bug.cgi?id=3066

Signed-off-by: Petri Savolainen <d528fd253b9aaf78fa72edbcc6249e82047f6ce6@linaro.org>
Reviewed-by: Brian Brooks <8e906ed46ccdc37d68771658f0f8f8740a374927@arm.com>
Signed-off-by: Maxim Uvarov <db4d16e02ae2d7493db430203537da8b2e34f290@linaro.org>

dkrot/odp,dkrot/odp,dkrot/odp,dkrot/odp