net: ipconfig: avoid warning by making ic_addrservaddr static

The symbol ic_addrservaddr is not static, but has no declaration
to match so make it static to fix the following warning:

net/ipv4/ipconfig.c:130:8: warning: symbol 'ic_addrservaddr' was not declared. Should it be static?
Signed-off-by: NBen Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/ipconfig.c

@@ -127,7 +127,7 @@ __be32 ic_myaddr = NONE;		/* My IP address */
 static __be32 ic_netmask = NONE;	/* Netmask for local subnet */
 __be32 ic_gateway = NONE;	/* Gateway IP address */
 
-__be32 ic_addrservaddr = NONE;	/* IP Address of the IP addresses'server */
+static __be32 ic_addrservaddr = NONE;	/* IP Address of the IP addresses'server */
 
 __be32 ic_servaddr = NONE;	/* Boot server IP address */