net: ieee802154: fix error return code in dgram_bind()

Fix to return error code -EINVAL from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: 94160108

 ("net/ieee802154: fix uninit value bug in dgram_sendmsg")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Link: https://lore.kernel.org/r/20220919160830.1436109-1-weiyongjun@huaweicloud.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>