net: ipv6: Add IPv6 build options

Add options to Makefile and Kconfig file to build IPv6

Series-changes: 3
- Added help for IPv6 support

Signed-off-by: Viacheslav Mitrofanov <v.v.mitrofanov@yadro.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/net/Makefile b/net/Makefile
index 4f757a2..00d6f9d 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -21,6 +21,7 @@
 obj-$(CONFIG_NET)      += eth_common.o
 obj-$(CONFIG_CMD_LINK_LOCAL) += link_local.o
 obj-$(CONFIG_NET)      += net.o
+obj-$(CONFIG_IPV6)     += net6.o
 obj-$(CONFIG_CMD_NFS)  += nfs.o
 obj-$(CONFIG_CMD_PING) += ping.o
 obj-$(CONFIG_CMD_PCAP) += pcap.o