firmware: always reset PHY when initializing Ethernet.

Fixes #897.

artiq/firmware/bootloader/main.rs

@@ -158,11 +158,8 @@ fn network_boot() {
 
     println!("Using MAC address {} and IP address {}", eth_addr, ip_addr);
 
-    #[allow(unused_mut)]
     let mut net_device = unsafe { ethmac::EthernetDevice::new() };
-
-    #[cfg(has_ethphy)]
-    net_device.reset_phy();
+    net_device.reset_phy_if_any();
 
     let mut neighbor_map = [None; 2];
     let neighbor_cache =

artiq/firmware/libboard/ethmac.rs

@@ -57,6 +57,11 @@ impl EthernetDevice {
             clock::spin_us(2_000);
         }
     }
+
+    pub fn reset_phy_if_any(&mut self) {
+        #[cfg(has_ethphy)]
+        self.reset_phy();
+    }
 }
 
 impl<'a> Device<'a> for EthernetDevice {

artiq/firmware/runtime/main.rs

@@ -150,7 +150,8 @@ fn startup_ethernet() {
         }
     }
 
-    let net_device = unsafe { ethmac::EthernetDevice::new() };
+    let mut net_device = unsafe { ethmac::EthernetDevice::new() };
+    net_device.reset_phy_if_any();
 
     // fn _net_trace_writer<U>(timestamp: u64, printer: smoltcp::wire::PrettyPrinter<U>)
     //         where U: smoltcp::wire::pretty_print::PrettyPrint {