openntpd: use correct step override method

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/openntpd/openntpd.mk

@@ -9,11 +9,10 @@ OPENNTPD_SITE = ftp://ftp.openbsd.org/pub/OpenBSD/OpenNTPD
 OPENNTPD_CONF_OPT = --with-builtin-arc4random --disable-strip
 OPENNTPD_INSTALL_TARGET_OPT = DESTDIR=$(TARGET_DIR) install
 
-$(eval $(call AUTOTARGETS,package,openntpd))
-
-$(OPENNTPD_TARGET_UNINSTALL):
-	$(call MESSAGE,"Uninstalling")
+define OPENNTPD_UNINSTALL_TARGET_CMDS
 	rm -f $(TARGET_DIR)/usr/sbin/ntpd
 	rm -f $(TARGET_DIR)/etc/ntpd.conf
 	rm -f $(TARGET_DIR)/usr/share/man/man?/ntpd*
-	rm -f $(OPENNTPD_TARGET_INSTALL_TARGET) $(OPENNTPD_HOOK_POST_INSTALL)
+endef
+
+$(eval $(call AUTOTARGETS,package,openntpd))