firmware: WDK: Improve false-positive detection

src/binwalk/magic/firmware

@@ -446,9 +446,12 @@
 
 # Found in DIR-100 firmware
 0       string      AIH0        AIH0 firmware header, header size: 48,
->12     belong      x           size: %d,
->8      belong      !0          executable code,
->>8     belong      x           load address: 0x%X,
+>12     ubelong     0           {invalid}
+>12     ubelong+48  x           {size:%d}
+>12     ubelong+48  x           size: %d,
+>8      ubelong     !0          executable code,
+>>8     ubelong&3   !0          {invalid}
+>>8     ubelong     x           load address: 0x%X,
 >32     string      x           version: "%s"
 
 0       belong      0x5EA3A417      SEAMA firmware header, big endian,