MIPS: remove Micronas VCT boards

The deadline for migration to CONFIG_DM is v2020.01. The VCT
baords would need an almost complete rewrite of all drivers to
support driver model.

Unless someone has access to the hardware and volunteers to do the migration,
the board should be scheduled for removal.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Acked-by: Stefan Roese <sr@denx.de>