cmd/frps: update help info

src/frp/cmd/frps/main.go

@@ -46,6 +46,7 @@ Options:
 	-L log_file               set output log file, including console
 	--log-level=<log_level>   set log level: debug, info, warn, error
 	--addr=<bind_addr>        listen addr for client, example: 0.0.0.0:7000
+	--reload				  reload ini file and configures in common section won't be changed
 	-h --help                 show this screen
 	-v --version              show version
 `