SDK UART driver example with hardware flow control

[#1]

Overview
========
The LPUART example for FreeRTOS demonstrates the possibility to use the LPUART driver in the RTOS
with hardware flow control. The example uses two instances of LPUART IP and sends data 
between them. The UART signals must be jumpered together on the board.

Toolchain supported
===================
- MCUXpresso 11.0.0

Hardware requirements
=====================
- Mini/micro USB cable
- MIMXRT1050-EVKB board
- Personal Computer

Board settings
==============
R278 and R279 must be populated, or have pads shorted. These resistors are under the display 
opposite side of board from uSD connector.

The following pins need to be jumpered together:

---------------------------------------------------------------------------------
| | UART3 (UARTA) | UART8 (UARTB) |
|---|-------------------------------------|-------------------------------------|
| # | Signal | Function | Jumper | Jumper | Function | Signal |
|---|---------------|----------|----------|----------|----------|---------------|
| 1 | GPIO_AD_B1_07 | RX | J22-pin1 | J23-pin1 | TX | GPIO_AD_B1_10 |
| 2 | GPIO_AD_B1_06 | TX | J22-pin2 | J23-pin2 | RX | GPIO_AD_B1_11 |
| 3 | GPIO_AD_B1_04 | CTS | J23-pin3 | J24-pin5 | RTS | GPIO_SD_B0_03 |
| 4 | GPIO_AD_B1_05 | RTS | J23-pin4 | J24-pin4 | CTS | GPIO_SD_B0_02 |
---------------------------------------------------------------------------------


Prepare the Demo
================
1. Connect a USB cable between the host PC and the OpenSDA USB port on the target board.
2. Open a serial terminal with the following settings:
 - 115200 baud rate
 - 8 data bits
 - No parity
 - One stop bit
 - No flow control
3. Download the program to the target board.
4. Either press the reset button on your board or launch the debugger in your IDE to begin running the demo.

Running the demo
================
You will see status of the example printed to the console.

Customization options
=====================