crypto: marvell/cesa - always ensure mid-fragments after first-fragment

If we add a template first-fragment operation, always update the
template to be a mid-fragment.  This ensures that mid-fragments
always follow on from a first fragment in every case.

This means we can move the first to mid-fragment update code out of
mv_cesa_ahash_dma_add_data().

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>