net/sched: taprio: always validate TCA_TAPRIO_ATTR_PRIOMAP

In the Linux kernel, the following vulnerability has been resolved: net/sched: taprio: always validate TCA_TAPRIO_ATTR_PRIOMAP If one TCA_TAPRIO_ATTR_PRIOMAP attribute has been provided, taprio_parse_mqprio_opt() must validate it, or userspace can inject arbitrary data to the kernel, the second time taprio_change() is called. First call (with valid attributes) sets dev->num_tc to a non zero value. Second call (with arbitrary mqprio attributes) returns early from taprio_parse_mqprio_opt() and bad things can happen.