drivers/crypto: use ring size function

drivers/crypto: use ring size function

Rather than reading the size directly from the ring structure, use the
dedicated ring function for that purpose.
Previous commits to do this only did so for the null crypto driver which
was the only one compiled in by default, but all other drivers need to be
similarly updated.

Fixes: b11c78a2e0c6 ("crypto/null: use ring size function")

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>