crypto: octeontx2 - add support to get engine capabilities

Adds support to get engine capabilities and adds a new mailbox
to share capabilities with VF driver.

Signed-off-by: Suheil Chandran <schandran@marvell.com>
Signed-off-by: Srujana Challa <schalla@marvell.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>