transmission: correct gtk dependencies after NLS rework

With the recent NLS rework, BR2_ENABLE_NLS doesn't imply the absense of --disable-nls, so
configure may fail with:

configure: error: "The gtk client cannot be built without nls support.  Try adding either --enable-nls or --without-gtk"

So adjust the dependencies to use BR2_SYSTEM_ENABLE_NLS instead.

As mentioned by Arnout, an alternative solution could be to explicitly pass
--enable-nls as the stub functions are now available everywhere - But I went
with the dependency for consistency reasons.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/transmission/Config.in

@@ -39,12 +39,12 @@ config BR2_PACKAGE_TRANSMISSION_REMOTE
 
 config BR2_PACKAGE_TRANSMISSION_GTK
 	bool "transmission-gtk"
-	depends on BR2_PACKAGE_LIBGTK3 && BR2_ENABLE_LOCALE
+	depends on BR2_PACKAGE_LIBGTK3 && BR2_SYSTEM_ENABLE_NLS
 	help
 	  Install transmission GTK-based GUI interface.
 
-comment "transmission-gtk needs a toolchain w/ locale"
-	depends on BR2_PACKAGE_LIBGTK3 && !BR2_ENABLE_LOCALE
+comment "transmission-gtk needs NLS enabled"
+	depends on BR2_PACKAGE_LIBGTK3 && !BR2_SYSTEM_ENABLE_NLS
 endif
 
 comment "transmission needs a toolchain w/ threads"