kf5-modemmanager-qt: correct dependencies comment display conditions

Display the dependencies comment only when modem-manager is enabled.
Otherwise, a toolchain configuration change would not make the package
selectable.

Cc: Pierre Ducroquet <pinaraf@pinaraf.info>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/kf5/kf5-modemmanager-qt/Config.in

@@ -16,4 +16,5 @@ config BR2_PACKAGE_KF5_MODEMMANAGER_QT
 
 comment "kf5-modemmanager-qt needs toolchain w/ threads"
 	depends on BR2_USE_MMU
+	depends on BR2_PACKAGE_MODEM_MANAGER
 	depends on !BR2_TOOLCHAIN_HAS_THREADS