OS_IS_FREERTOS not actually defined in build output

[jwolfm98]

https://github.com/Xilinx/embeddedsw/blob/0f463342b5c42ff17690d396fb74381fb13168ab/ThirdParty/sw_services/lwip220/src/lwip-2.2.0/contrib/ports/xilinx/netif/xadapter.c#L198

Given the lack of usage of this macro, I just changed it to !NO_SYS, now it works.

Also.... Consider that the priority setting here basically means it never executes. It should either be driven on a interrupt thats driven by link status if possible, or the highest priority with a default 5 second delay that's configurable.