umdns: add missing syscalls to seccomp filter

The 'mmap', 'mmap2', 'munmap' syscalls are missing.
Found with 'utrace /usr/sbin/umdns'.

Signed-off-by: Ronny Kotzschmar <[email protected]>

package/network/services/umdns/files/umdns.json

@@ -20,6 +20,9 @@
 				"fstat",
 				"getsockname",
 				"ioctl",
+				"mmap",
+				"mmap2",
+				"munmap",
 				"open",
 				"openat",
 				"pipe",