ARC: [plat-hsdk] Switch DisplayLink driver from fbdev to DRM

Currently there're 2 different implementations of the driver for
DisplayLink USB2.0-to-HDMI/DVI adapters: older FBDEV and modern true
DRM.

We initially decided to use FBDEV version just because with it
/dev/fbX is usable from user-space while in DRM version
with DRM_FBDEV_EMULATION user-space cannot draw anything on a real
screen, for more info read [1].

But today /dev/fbX is not that important as more and more software
projects switch to use of DRI (/dev/dri/cardX).

But what's even more important DRM driver allows building of complicated
graphics processing chains. The most important for us is rendering of
3D on a dedicated GPU while outputting video through a simpler
bitstreamer like DisplayLink. So let's use much more future-proof
driver from now on.

[1] https://lists.freedesktop.org/archives/dri-devel/2017-December/159519.html



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