HDFS-10907. Fix Erasure Coding documentation. Contributed by Manoj Govindassamy.

hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSCommands.md

@@ -463,7 +463,7 @@ Runs the diskbalancer CLI. See [HDFS Diskbalancer](./HDFSDiskbalancer.html) for
 Usage:
 
        hdfs erasurecode [generic options]
-         [-setPolicy [-s <policyName>] <path>]
+         [-setPolicy [-p <policyName>] <path>]
          [-getPolicy <path>]
          [-listPolicies]
          [-usage [cmd ...]]

hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSErasureCoding.md

@@ -125,7 +125,7 @@ Below are the details about each command.
 
       `path`: An directory in HDFS. This is a mandatory parameter. Setting a policy only affects newly created files, and does not affect existing files.
 
-      `policyName`: The ErasureCoding policy to be used for files under this directory. This is an optional parameter, specified using ‘-s’ flag. If no policy is specified, the system default ErasureCodingPolicy will be used.
+      `policyName`: The ErasureCoding policy to be used for files under this directory. This is an optional parameter, specified using ‘-p’ flag. If no policy is specified, the system default ErasureCodingPolicy will be used.
 
  *  `[-getPolicy <path>]`