pktgen: Require CONFIG_INET due to use of IPv4 checksum function

Unlike for IPv6, the IPv4 checksum functions are only available
if CONFIG_INET is set.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/Kconfig

@@ -281,7 +281,7 @@ menu "Network testing"
 
 config NET_PKTGEN
 	tristate "Packet Generator (USE WITH CAUTION)"
-	depends on PROC_FS
+	depends on INET && PROC_FS
 	---help---
 	  This module will inject preconfigured packets, at a configurable
 	  rate, out of a given interface.  It is used for network interface