add option to set LLDP transmit delay, hold timers to set update frequency
Signed-off-by: Stephen Howell <howels@allthatwemight.be>
(cherry picked from commit a5f715da71)
Link: https://github.com/openwrt/openwrt/pull/15299
Signed-off-by: Robert Marko <robimarko@gmail.com>