libnet: Correctly re-initialize the "ip_version" variable each time

I recently noticed that if you start QEMU with two NICs, and only
want to boot from the second NIC, SLOF only tries to get an IP
address via DHCPv6 instead of trying both, DHCPv4 and DHCPv6. For
example:

$ qemu-system-ppc64 -nic hubport,hubid=1 \
    -nic user,model=virtio,tftp=/.../tftp,bootfile=zImage.pseries
[...]
Trying to load:  from: /vdevice/l-lan@71000002 ...
 Initializing NIC
  Reading MAC address from device: 52:54:00:12:34:56
  Requesting information via DHCP:  007
Aborted

E3001 (net) Could not get IP address
Trying to load:  from: /pci@800000020000000/ethernet@0 ...
 Initializing NIC
  Reading MAC address from device: 52:54:00:12:34:57
  Requesting information via DHCPv6: done
  Using IPv6 address: fec0::5254:ff:fe12:3457

The problem is that we never re-initialize the "ip_version" variable
anymore, so once it has been set to 6, it stays at 6 for the second
network boot attempt, too. Thus reset the variable to 4 at the beginning
of the netload() function.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

lib/libnet/netload.c

@@ -38,7 +38,7 @@
 #define MAX_PKT_SIZE         1720
 #define DEFAULT_BOOT_RETRIES 10
 #define DEFAULT_TFTP_RETRIES 20
-static int ip_version = 4;
+static int ip_version;
 
 typedef struct {
 	char filename[100];
@@ -542,6 +542,8 @@ int netload(char *buffer, int len, char *args_fs, int alen)
 	uint8_t own_mac[6];
 	char *pkt_buffer;
 
+	ip_version = 4;
+
 	pkt_buffer = SLOF_alloc_mem(MAX_PKT_SIZE);
 	if (!pkt_buffer) {
 		puts("ERROR: Unable to allocate memory");