systemd: fix -Dlibidn2 option when libidn2 is not available

Commit 4ded5d6af4f0198036183f00de190569d7578bc3 ("systemd: add
optional dependency on libidn2") contained a mistake: -Dlibidn2=true
was passed even when neither libidn nor libidn2 are
available. Obviously it should be -Dlibidn2=false.

Reported-by: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/systemd/systemd.mk

@@ -83,7 +83,7 @@ else ifeq ($(BR2_PACKAGE_LIBIDN),y)
 SYSTEMD_DEPENDENCIES += libidn
 SYSTEMD_CONF_OPTS += -Dlibidn=true -Dlibidn2=false
 else
-SYSTEMD_CONF_OPTS += -Dlibidn=false -Dlibidn2=true
+SYSTEMD_CONF_OPTS += -Dlibidn=false -Dlibidn2=false
 endif
 
 ifeq ($(BR2_PACKAGE_LIBSECCOMP),y)