crypto: qce - Set data unit size to message length for AES XTS transformation

Set the register REG_ENCR_XTS_DU_SIZE to cryptlen for AES XTS
transformation. Anything else causes the engine to return back
wrong results.

Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>