Reset TCP/IP connection with a '+' prefix

When running scrcpy with --tcpip=xx.xx.xx.xx, to make sure a new working
connection is established, it was first disconnected by a call to:

    adb disconnect <addr>

However, this caused all running instances connected to that address to
be killed. Running several instances of scrcpy on the same device is now
useful with virtual displays, so change the default behavior to NOT
disconnect.

To force a reconnection, a '+' prefix can be added:

    scrcpy --tcpip=+192.168.0.x

Fixes #5562 <https://github.com/Genymobile/scrcpy/issues/5562>

app/src/cli.c

@@ -860,16 +860,17 @@ static const struct sc_option options[] = {
     {
         .longopt_id = OPT_TCPIP,
         .longopt = "tcpip",
-        .argdesc = "ip[:port]",
+        .argdesc = "[+]ip[:port]",
         .optional_arg = true,
-        .text = "Configure and reconnect the device over TCP/IP.\n"
+        .text = "Configure and connect the device over TCP/IP.\n"
                 "If a destination address is provided, then scrcpy connects to "
                 "this address before starting. The device must listen on the "
                 "given TCP port (default is 5555).\n"
                 "If no destination address is provided, then scrcpy attempts "
                 "to find the IP address of the current device (typically "
                 "connected over USB), enables TCP/IP mode, then connects to "
-                "this address before starting.",
+                "this address before starting.\n"
+                "Prefix the address with a '+' to force a reconnection.",
     },
     {
         .longopt_id = OPT_TIME_LIMIT,