replace ndo_set_multicast_list with ndo_set_rx_mode

for kernels >= 3.2.0

read:
commit b81693d9149c598302e8eb9c20cb20330d922c8e
commit afc4b13df143122f99a0eb10bfefb216c2806de0
include linux/module.h where needed

needed for the "THIS_MODULE", "EXPORT_SYMBOL" and co. macros.
linux/module.h needs to be explicitly included since the big header
cleanup around kernel version 3.2.0
updated README with working kernel versions