crypto: qce - use __free() for a buffer that's always freed

The buffer allocated in qce_ahash_hmac_setkey is always freed before
returning to use __free() to automate it.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>