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/colibri_t20_defconfig b/configs/colibri_t20_defconfig
index e652ebc..8247248 100644
--- a/configs/colibri_t20_defconfig
+++ b/configs/colibri_t20_defconfig
@@ -36,6 +36,7 @@
 CONFIG_OF_LIVE=y
 CONFIG_DEFAULT_DEVICE_TREE="tegra20-colibri"
 CONFIG_ENV_IS_IN_NAND=y
+CONFIG_IP_DEFRAG=y
 CONFIG_SPL_DM=y
 CONFIG_DFU_MMC=y
 CONFIG_DFU_RAM=y