crypto/aesni_gcm: support in-place chained mbufs

crypto/aesni_gcm: support in-place chained mbufs

IPSec Multi buffer library supports encryption on multiple segments.
When dealing with chained buffers (multiple segments), as long as
the operation is in-place, the destination buffer does not have to
be contiguous (unlike in the case of out-of-place operation).
Therefore, the limitation of not supporting in-place chained mbuf
can be removed.

Signed-off-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>