This adds a patch for ser2net, so that ser2net can be configured
to flash leds on serial traffic. This could -for example- be used
to have an activity indicator, like netdev trigger.
Internally, the linux kernel's 'transient' led trigger is used.

Signed-off-by: Michael Heimpold <mhei@heimpold.de>

 - update to latest version (v2.10.0)
 - add a patch to fix compilation failures due to missing TIOCSRS485 macro
 - add license info
 - add myself as maintainer

Signed-off-by: Nicolas Thill <nico@openwrt.org>