net: dsa: make NET_DSA manually selectable from the config

Change bd76a11670 made all DSA drivers
depend on NET_DSA rather than selecting them. However, as the only way
to select this option was to actually select a driver, it made DSA
impossible to enable at all.

This patch adds an explicit entry which the user will have to enable
prior selecting a driver.

Signed-off-by: Mathieu Olivari <mathieu@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/Kconfig

@@ -5,9 +5,12 @@ config HAVE_NET_DSA
 # Drivers must select NET_DSA and the appropriate tagging format
 
 config NET_DSA
-	tristate
+	tristate "Distributed Switch Architecture"
 	depends on HAVE_NET_DSA && NET_SWITCHDEV
 	select PHYLIB
+	---help---
+	  Say Y if you want to enable support for the hardware switches supported
+	  by the Distributed Switch Architecture.
 
 if NET_DSA