ARM: mvebu: convert Globalscale Mirabox to PBL_MULTI_IMAGES

This converts Marvell Armada 370 based Globalscale Mirabox
to PBL_MULTI_IMAGES. A DT overlay is added to keep possible
barebox-specific changes separated and added to lowlevel
board init.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
ARM: mvebu: convert Marvell Armada XP GP to PBL_MULTI_IMAGES

This converts Marvell Armada XP based Marvell Armada XP GP
to PBL_MULTI_IMAGES. A DT overlay is added to keep possible
barebox-specific changes separated and added to lowlevel
board init.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
ARM: mvebu: convert PlatHome Openblocks AX3-4 to PBL_MULTI_IMAGES

This converts Marvell Armada XP based PlatHome Openblocks AX3-4
to PBL_MULTI_IMAGES. A DT overlay is added to keep possible
barebox-specific changes separated and added to lowlevel
board init.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
ARM: mvebu: convert to multiple board selection

With all SoCs converted to DT based probing, select
PBL_MULTI_IMAGES support and get rid of SoCs Kconfig
choice to allow multiple boards to be selected.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
ARM: mvebu: remove dtb Makefile entries

MULTI_PBL images have a built-in dtb by default. With all MVEBU
SoCs converted to MULTI_PBL images, get rid of the extra Makefile
rules for appended dtbs.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>