rtlwifi: Fix breakage in debug functions when built as a module

Since commit 481b9606, it has not been possible to invoke debugging
with any rtlwifi driver built as a module.

Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rtlwifi/Kconfig b/drivers/net/wireless/rtlwifi/Kconfig
index 44b9c0a..cefac6a 100644
--- a/drivers/net/wireless/rtlwifi/Kconfig
+++ b/drivers/net/wireless/rtlwifi/Kconfig
@@ -50,7 +50,7 @@
 	default m
 
 config RTLWIFI_DEBUG
-	tristate "Additional debugging output"
+	bool "Additional debugging output"
 	depends on RTL8192CE || RTL8192CU || RTL8192SE || RTL8192DE
 	default y