treewide: Migrate CONFIG_TSEC_ENET to Kconfig

Migrate the CONFIG_TSEC_ENET option to Kconfig.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index 608ed71..f2cfcb0 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -411,4 +411,11 @@
 	help
 	  QBman fixups to allow deep sleep in DPAA 1 SOCs
 
+config TSEC_ENET
+	select PHYLIB
+	bool "Enable Three-Speed Ethernet Controller"
+	help
+	  This driver implements support for the (Enhanced) Three-Speed
+	  Ethernet Controller found on Freescale SoCs.
+
 endif # NETDEVICES