crypto: caam - fix HW S/G in ablkcipher_giv_edesc_alloc()

HW S/G generation does not work properly when the following conditions
are met:
-src == dst
-src/dst is S/G
-IV is right before (contiguous with) the first src/dst S/G entry
since "iv_contig" is set to true (iv_contig is a misnomer here and
it actually refers to the whole output being contiguous)

Fix this by setting dst S/G nents equal to src S/G nents, instead of
leaving it set to init value (0).

Signed-off-by: Horia Geantă <horia.geanta@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>