crypto: omap-sham - initialize req only after omap_sham_hw_init()

Let's only initialize dd->req after omap_sham_hw_init() in case of
errors.

Looks like leaving dd->req initialized on omap_sham_hw_init() errors is
is not causing issues though as we return on errors. So this patch can be
applied as clean-up.

Cc: Lokesh Vutla <lokeshvutla@ti.com>
Cc: Tero Kristo <kristo@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>