arm64: mvebu: Rename db-88f7040 files to armada-8k

arm64: mvebu: Rename db-88f7040 files to armada-8k

This moves some of the Armada DB-88F7040 board specific files to a more
generic name: armada-8k. This is in preparation for the Armada-8k
support which will be added soon. And since both platforms share
most devices, lets also share most source files to not duplicate
the code here.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Nadav Haklai <nadavh@marvell.com>
Cc: Neta Zur Hershkovits <neta@marvell.com>
Cc: Kostya Porotchkin <kostap@marvell.com>
Cc: Omri Itach <omrii@marvell.com>
Cc: Igal Liberman <igall@marvell.com>
Cc: Haim Boot <hayim@marvell.com>
Cc: Hanna Hawa <hannah@marvell.com>