crypto: omap-sham - rename sgl to sgl_tmp for deprecation

The current usage of sgl will be deprecated, and will be replaced by an
array required by the sg based driver implementation. Rename the existing
variable as sgl_tmp so that it can be removed from the driver easily later.

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