crypto: stm32 - use the new scatterwalk functions

Replace calls to the deprecated function scatterwalk_copychunks() with
memcpy_from_scatterwalk(), memcpy_to_scatterwalk(), scatterwalk_skip(),
or scatterwalk_start_at_pos() as appropriate.

Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Maxime Méré <maxime.mere@foss.st.com>
Cc: Thomas Bourgoin <thomas.bourgoin@foss.st.com>
Cc: linux-stm32@st-md-mailman.stormreply.com
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>