Ensure each serial port has enough buffer space to write out the largest

MSP response.

src/main/drivers/serial_uart.h

@@ -21,10 +21,10 @@
 // Code is optimal when buffer sizes are powers of 2 due to use of % and / operators.
 #define UART1_RX_BUFFER_SIZE    256
 #define UART1_TX_BUFFER_SIZE    256
-#define UART2_RX_BUFFER_SIZE    128
-#define UART2_TX_BUFFER_SIZE    64
-#define UART3_RX_BUFFER_SIZE    128
-#define UART3_TX_BUFFER_SIZE    64
+#define UART2_RX_BUFFER_SIZE    256
+#define UART2_TX_BUFFER_SIZE    256
+#define UART3_RX_BUFFER_SIZE    256
+#define UART3_TX_BUFFER_SIZE    256
 
 typedef struct {
     serialPort_t port;