crypto: omap-aes - PIO mode: platform data for OMAP4/AM437x and trigger

We initialize the scatter gather walk lists needed for PIO mode and avoid all
DMA paths such as mapping/unmapping buffers by checking for the pio_only flag.

Signed-off-by: Joel Fernandes <joelf@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>