vl.c: Check the asked ram_size later. As a Xen guest can have more than 2GB of RAM on a 32bit host, we move the conditions after than we now if we run one Xen or not. [agraf] separate xen branch from ram_size check Signed-off-by: Anthony PERARD <anthony.perard@citrix.com> Signed-off-by: Alexander Graf <agraf@suse.de>