crypto: omap-sham - split up data to multiple sg elements with huge data

When using huge data amount, allocating free pages fails as the kernel
isn't able to process get_free_page requests larger than MAX_ORDER.
Also, the DMA subsystem has an inherent limitation that data size
larger than some 2MB can't be handled properly. In these cases,
split up the data instead to smaller requests so that the kernel
can allocate the data, and also so that the DMA driver can handle
the separate SG elements.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Tested-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>