buildroot

configs: add ARC HS38 VDK virtual boards

Virtualizer Development Kits (VDKs) are software development kits
containing design-specific virtual prototypes as well as debug and
analysis tools and sample software.

With this change we add support for VDK based on ARC HS38 core.

Note that FS-overlay is required to allow instantiation of console on
both serial port and LCD screen simultaneously.

Cc: Peter Korsgaard <peter@korsgaard.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>