net: Convert CONFIG_IP_DEFRAG to Kconfig

Convert CONFIG_IP_DEFRAG to Kconfig, update defconfigs, headers
and whitelist. This patch is a follow-up on a patch by Christian
Gmeiner with the added config/header/whitelist updates.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Reported-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/configs/tools-only_defconfig b/configs/tools-only_defconfig
index fb06076..aa73661 100644
--- a/configs/tools-only_defconfig
+++ b/configs/tools-only_defconfig
@@ -9,6 +9,7 @@
 CONFIG_OF_CONTROL=y
 CONFIG_OF_HOSTFILE=y
 CONFIG_DEFAULT_DEVICE_TREE="sandbox"
+CONFIG_IP_DEFRAG=y
 # CONFIG_UDP_FUNCTION_FASTBOOT is not set
 CONFIG_SANDBOX_GPIO=y
 CONFIG_DM_I2C_COMPAT=y