Revert "net/ieee802154: reject zero-sized raw_sendmsg()"

This reverts commit 3a4d061c

.

There is a v2 which does return zero if zero length is given.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20221005014750.3685555-1-aahringo@redhat.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>