[docs] fix normal fpclass mask

Author: nunoplopes

llvm/docs/LangRef.rst

@@ -1527,7 +1527,7 @@ Currently, only the following parameter attributes are defined:
     +-------+----------------------+---------------+
     |  inf  | +/- infinity         |      516      |
     +-------+----------------------+---------------+
-    |  norm | +/- normal           |       26      |
+    |  norm | +/- normal           |      264      |
     +-------+----------------------+---------------+
     |  sub  | +/- subnormal        |      144      |
     +-------+----------------------+---------------+