crypto: bcm - check assoclen for rfc4543/rfc4106

Validated assoclen for RFC4543 which expects an assoclen
of 16 or 20, the same as RFC4106.
Based on seqiv, IPsec ESP and RFC4543/RFC4106 the assoclen is sizeof
IP Header (spi, seq_no, extended seq_no) and IV len. This can be 16 or
20 bytes.

Signed-off-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>