crypto: ccree - move key load desc. before flow desc.

Refactor the descriptor setup code in order to move the key loading
descriptor to one before last position. This has no effect on current
functionality but is needed for later support of Content Protection
Policy keys.

Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>