net, xdp: Correct grammar

Use the correct verb form in 2 places in the XDP rx-queue comment.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jesper Dangaard Brouer <hawk@kernel.org>
Link: https://lore.kernel.org/bpf/20231213043735.30208-1-rdunlap@infradead.org