hvc_console: Remove __devinit annotation from hvc_alloc

Virtio consoles can be hotplugged, so hvc_alloc gets called from
multiple sites: from the initial probe() routine as well as later on
from workqueue handlers which aren't __devinit code.

So, drop the __devinit annotation for hvc_alloc.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Cc: linuxppc-dev@ozlabs.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>