bmx7-dnsupdate: Call killall with the -s

Some versions of killall do support the `killall -SIGNAL` syntax and
have only `-s SIGNAL` which should be supported everywhere.

I see the problem with *killall (PSmisc) 23.3* on latest TurrisOS 5.2

Signed-off-by: Jan Baier <jan.baier@amagical.net>

utils/bmx7-dnsupdate/Makefile

@@ -2,7 +2,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=bmx7-dnsupdate
 PKG_VERSION:=0.1
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 
 include $(INCLUDE_DIR)/package.mk
 

utils/bmx7-dnsupdate/files/usr/bin/bmx7-dnsupdate

@@ -22,7 +22,7 @@ while true; do
 
     # reload dnsmasq to apply changes
     logger -t bmx7-dnsupdate "dnsmasq updated due to new hosts"
-    killall -HUP dnsmasq
+    killall -s HUP dnsmasq
 
     # block until originators changes
     inotifywait -e create -e delete -q /var/run/bmx7/json/originators/ || sleep 10