crypto - aesni: Add a synchronous version of gcm-aesni.

When we do IPsec NIC offloading, we need a fallback for
packets that were targeted to be IPsec offloaded but
rerouted to a device that does not support IPsec offload.
This patch adds a synchronous version of gcm-aesni so
that we don't need to fallback to a slow software
implementation of aes.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>