cryptodev: add function to retrieve device name

Currently, in order to get the name of a crypto device,
a user needs to access to it using the crypto device structure.

It is a better practise to have a function to retrieve this
name, given a device id.

Signed-off-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
Acked-by: Sergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com>