mac80211: silence warning for missing rate information (#3167)

Silence warnings for missing rate information.

These warnings do not provide value. Instead, they might rotate more
crucial information out of the kernel message ringbuffer.

Link: https://github.com/freifunk-gluon/gluon/issues/3160



Signed-off-by: David Bauer <mail@david-bauer.net>
(cherry picked from commit 8a4c553a4323b49199f11f951b00c60315e56026)

Co-authored-by: David Bauer <mail@david-bauer.net>