crypto: seqiv - remove seqiv_create()

seqiv_create() is pointless because it just checks that the template is
being instantiated as an AEAD, then calls seqiv_aead_create().  But
seqiv_aead_create() does the exact same check, via aead_geniv_alloc().

Just remove seqiv_create() and use seqiv_aead_create() directly.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>