[libFuzzer] Minor documentation fixes.

Author: Dor1s

llvm/docs/LibFuzzer.rst

@@ -250,15 +250,15 @@ still work.
 The most important command line options are:
 
 ``-help``
-  Print help message.
+  Print help message (``-help=1``).
 ``-seed``
   Random seed. If 0 (the default), the seed is generated.
 ``-runs``
   Number of individual test runs, -1 (the default) to run indefinitely.
 ``-max_len``
   Maximum length of a test input. If 0 (the default), libFuzzer tries to guess
   a good value based on the corpus (and reports it).
-``len_control``
+``-len_control``
   Try generating small inputs first, then try larger inputs over time.
   Specifies the rate at which the length limit is increased (smaller == faster).
   Default is 100. If 0, immediately try inputs with size up to max_len.