crypto: hisilicon - cleanup warning in qm_get_qos_value()

Building with clang static analysis returns this warning:

qm.c:4382:11: warning: The left operand of '==' is a garbage value
        if (*val == 0 || *val > QM_QOS_MAX_VAL || ret) {
            ~~~~ ^

The call to qm_qos_value_init() can return an error without setting
*val.  So check ret before checking *val.

Fixes: 72b010dc ("crypto: hisilicon/qm - supports writing QoS int the host")
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>