crypto: qce - Return unsupported if key1 and key 2 are same for AES XTS algorithm

Crypto engine does not support key1 = key2 for AES XTS algorithm; the
operation hangs the engines.  Return -EINVAL in case key1 and key2 are the
same.

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