linknx: fix name of PID file

Signed-off-by: Othmar Truniger <github@truniger.ch>

net/linknx/files/linknx.config

@@ -4,5 +4,5 @@ config daemon args
         #
         # typical example
         option conf '/etc/linknx.xml'
-        option options '-w --daemon=/tmp/linknx/linknx.log --pid-file=/var/run/linknx.log'
+        option options '-w --daemon=/tmp/linknx/linknx.log --pid-file=/var/run/linknx.pid'