arc: Add support for IoT development kit

The DesignWare ARC IoT Development Kit is a versatile platform
that includes the necessary hardware and software to accelerate
software development and debugging of sensor fusion,
voice recognition and face detection designs.

More information is avaialble here [1] and here [2].

The board is based on real silicon with
ARC EM9D-based Data Fusion IP Subsystem.

It sports a rich set of I/O including
 * DW USB OTG
 * DW MobileStorage (used for micro SD-card)
 * GPIO
 * multiple serial interface including DW APB UART
 * ADC, PWM and eFlash, SRAM and SPI Flash memory
 * Real-Time Clock (RTC)
 * Bluetooth module with worldwide regulatory compliance
   (FCC, IC, CE, ETSI, TELEC)
 * On-board 9-axis sensor (gyro, accelerometer and compass)

Extensible with Arduino, Pmod, mikroBUS connectors and a 2x18
extension header.

One of the most interesting features for developers is built-in
Digilent USB JTAG probe so only micro-USB cable is needed!

[1] https://www.synopsys.com/dw/ipdir.php?ds=arc_iot_development_kit
[2] https://www.synopsys.com/dw/doc.php/ds/cc/iot_dev_kit.pdf



Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>