net: buf: Use unified k_fifo API for FIFOs

Only net_receive() is using non-special value for net_buf_get_timeout
so this change is included here. Other users are using special values
which are already correctly handling ticks vs ms change.

Change-Id: Ib12d34ac5a546b36fa7b35615f082c82a256bd07
Signed-off-by: Szymon Janc <ext.szymon.janc@tieto.com>