debian mainline rt kernel 4.1: Problems with prussdrv and usb network

Hello everyone.
Recently I did an upgrade to the mainline rt kernel 4.1, following this instructions

The upgrade process went well and after boot I was unable to access the board via usb ethernet. In fact the interface shows up as eth2 on my linux box, so I typed ifconfig eth2 up
Access was regained but after a while the interface will loose the ip address. So I had to reissue the ifconfig eth2 up command time after time.

Another thing is that the pru was not enabled. This kernel has support for prussdrv? I tried to copy my old boneblack.dtb but I found out that it was not compatible… also I found two locations for dtb, one under /boot/dtbs and another at /boot/udev/dtbs… which one should I use?

Thank you very much

Carlos Novaes