Update serial and msp code to allow MSP on multiple ports.

Work in progress.  In testing using bluetooth on uart2 and uart1
connected to configurator it was observed that there is corrupted
responses being sent via uart2 - ez-gui shows some garbled data for the
box names.  updates appear sluggish in ez-gui but some correct data is
getting through.

Enabled with:

set serial_port_2_scenario = 8
save

src/main/io/serial.c

@@ -447,6 +447,15 @@ bool isSerialConfigValid(serialConfig_t *serialConfigToCheck)
         return false;
     }
 
+    uint8_t functionIndex;
+    uint8_t cliPortCount = 0;
+    for (functionIndex = 0; functionIndex < SERIAL_PORT_COUNT; functionIndex++) {
+        if (serialPortFunctions[functionIndex].scenario & FUNCTION_CLI) {
+            if (++cliPortCount > 1) {
+                return false;
+            }
+        }
+    }
     return true;
 }