doc: Document log_clear_flag RPC

Signed-off-by: Ben Walker <benjamin.walker@intel.com>
Change-Id: I70c2754a39a5f6a9cd4c6b78e818e7c9c46dcd8c
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/4255
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>

doc/jsonrpc.md

@@ -869,6 +869,43 @@ Example response:
 }
 ~~~
 
+## log_clear_flag {#rpc_log_clear_flag}
+
+Disable logging for specific portions of the application. The list of possible
+log flags can be obtained using the `log_get_flags` RPC and may be different
+for each application.
+
+### Parameters
+
+Name                    | Optional | Type        | Description
+----------------------- | -------- | ----------- | -----------
+flag                    | Required | string      | A log flag, or 'all'
+
+### Example
+
+Example request:
+
+~~~
+{
+  "jsonrpc": "2.0",
+  "method": "log_clear_flag",
+  "id": 1,
+  "params": {
+    "flag": "all"
+  }
+}
+~~~
+
+Example response:
+
+~~~
+{
+  "jsonrpc": "2.0",
+  "id": 1,
+  "result": true
+}
+~~~
+
 ## log_enable_timestamps {#rpc_log_enable_timestamps}
 
 Enable or disable timestamps.