Merge tag 'arc-more-fixes-for-2020.07-rc1' of https://gitlab.denx.de/u-boot/custodians/u-boot-arc

Here we introduce new development platfrom for ARC: HSDK 4xD.
That's pretty much the same base-board as in HSDK but with
very recent quad-core ARC HS47D in the ASIC.

Thus we try to re-use existing code as much as possible while
inevitably add some pieces needed for the new ASIC.

Also we drop selection of bounce buffers on AXS10x
as there's no use of them any longer.