net: remove NICInfo.bootable field

It is just set by net_set_boot_mask() and never used. The logic for rom loading
changed a lot since this field was introduced. It is not needed anymore.
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>
Acked-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

net.c

@@ -1207,7 +1207,6 @@ void net_set_boot_mask(int net_boot_mask)
 
     for (i = 0; i < nb_nics; i++) {
         if (net_boot_mask & (1 << i)) {
-            nd_table[i].bootable = 1;
             net_boot_mask &= ~(1 << i);
         }
     }

net.h

@@ -132,7 +132,6 @@ struct NICInfo {
     VLANState *vlan;
     VLANClientState *netdev;
     int used;
-    int bootable;
     int nvectors;
 };