nixos/initrd: improve descriptions

The improved lspci command shows all available ethernet controllers and
their kernel modules. Previously, the user had to provide the slot name
of a specific device.

nixos/modules/system/boot/initrd-network.nix

@@ -45,7 +45,8 @@ in
         is acquired using DHCP.
 
         You should add the module(s) required for your network card to
-        boot.initrd.availableKernelModules. lspci -v -s <ethernet controller>
+        boot.initrd.availableKernelModules.
+        <literal>lspci -v | grep -iA8 'network\|ethernet'</literal>
         will tell you which.
       '';
     };