cpumap: Zero-initialise xdp_rxq_info struct before running XDP program

In the Linux kernel, the following vulnerability has been resolved: cpumap: Zero-initialise xdp_rxq_info struct before running XDP program When running an XDP program that is attached to a cpumap entry, we don't initialise the xdp_rxq_info data structure being used in the xdp_buff that backs the XDP program invocation. Tobias noticed that this leads to random values being returned as the xdp_md->rx_queue_index value for XDP programs running in a cpumap. This means we're basically returning the contents of the uninitialised memory, which is bad. Fix this by zero-initialising the rxq data structure before running the XDP program.