lib/route: adjust coding style
lib/route: adjust coding style

I don't think that we should do "yoda conditions". Also, I wouldn't
compare pointers against NULL in a boolean context.

Obviously, this is a matter of opinions and no hard rules. However,
this seems consistent with what we otherwise do already.

thom311/libnl,greearb/libnl-ct,thom311/libnl,thom311/libnl,greearb/libnl-ct,greearb/libnl-ct