drivers/net/ethernet: Add ethernet dir and config option

This is the initial patch to organize the drivers/net directory
structure and networking device driver config options.  This patch
does the following:
  - add drivers/net/ethernet/Kconfig
  - integrate the new files into the existing config

Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index 8d0314d..5b95796 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -193,6 +193,8 @@
 #	Ethernet
 #
 
+source "drivers/net/ethernet/Kconfig"
+
 menuconfig NET_ETHERNET
 	bool "Ethernet (10 or 100Mbit)"
 	depends on !UML