iwlwifi: allow selecting only MVM driver

Now that we have two drivers (DVM and MVM) stop selecting
the DVM one (but make it default) and allow enabling only
the MVM driver if so desired. Add a warning for the case
of having neither DVM nor MVM enabled -- that's useless.
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/iwlwifi/Kconfig

@@ -6,7 +6,6 @@ config IWLWIFI
 	select LEDS_CLASS
 	select LEDS_TRIGGERS
 	select MAC80211_LEDS
-	select IWLDVM
 	---help---
 	  Select to build the driver supporting the:
 
@@ -45,6 +44,7 @@ config IWLWIFI
 config IWLDVM
 	tristate "Intel Wireless WiFi DVM Firmware support"
 	depends on IWLWIFI
+	default IWLWIFI
 	help
 	  This is the driver supporting the DVM firmware which is
 	  currently the only firmware available for existing devices.
@@ -58,6 +58,9 @@ config IWLMVM
 
 	  Say yes if you have such a device.
 
+comment "WARNING: iwlwifi is useless without IWLDVM or IWLMVM"
+	depends on IWLWIFI && IWLDVM=n && IWLMVM=n
+
 menu "Debugging Options"
 	depends on IWLWIFI