automation: qemu-smoke-arm64.sh: Increase RAM size

automation: qemu-smoke-arm64.sh: Increase RAM size

In the follow-up patch we will add new jobs using debug Xen builds.
Because the debug builds take more space and we might end up in
a situation when there is not enough free space (especially during
a static memory test that reserves some region in the middle), increase
RAM size for QEMU from 1GB to 2GB.

Signed-off-by: Michal Orzel <michal.orzel@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>