archs38: add HSDK board

archs38: add HSDK board

Synopsys DesignWare HSDK (which stands for ARC HS
Development Kit) is the latest and greatest development
platform that sports quad-core ARC HS38 in real silicon.

Most noticeable features of the board are:
 * Quad-core ARC HS38 CPU running at 1GHz
 * 4Gb of DDR
 * Built-in Vivante GPU (well supported via open source
   Etnaviv drivers)
 * Built-in Wi-Fi/Bluetooth module (RedPine RS-9113)

And as usual we have:
 * [micro] SD-card slot
 * 2 USB 2.0 ports
 * 1Gbit Ethernet port
 * Built-in Digilent JTAG probe
 * Serial port accessible via micro-USB port

For more information about HSDK board visit:
https://www.synopsys.com/dw/ipdir.php?ds=arc-hs-development-kit

Signed-off-by: Evgeniy Didin <[email protected]>
CC: Alexey Brodkin <[email protected]>
CC: Hauke Mehrtens <[email protected]>
CC: John Crispin <[email protected]>