ipconfig: fix trivial build error

The commit 5e953778 ("ipconfig: add nameserver
IPs to kernel-parameter ip=") introduces ic_nameservers_predef() that defined
only for BOOTP. However it is used by ip_auto_config_setup() as well. This
patch moves it outside of #ifdef BOOTP.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Christoph Fritz <chf.fritz@googlemail.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>