crypto: talitos - implement cra_priority

SEC1 doesn't have IPSEC_ESP descriptor type but it is able to perform
IPSEC using HMAC_SNOOP_NO_AFEU, which is also existing on SEC2
In order to be able to define descriptors templates for SEC1 without
breaking SEC2+, we have to give lower priority to HMAC_SNOOP_NO_AFEU
so that SEC2+ selects IPSEC_ESP and not HMAC_SNOOP_NO_AFEU which is
less performant.

This is done by adding a priority field in the template. If the field
is 0, we use the default priority, otherwise we used the one in the
field.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>