arm: plat-orion: only build addr-map.c when needed

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For now, addr-map.c is needed by all 5 Marvell EBU
sub-architectures. However, we are going to introduce the orion-mbus
driver, which will replace the address decoding code from
addr-map.c. In order to ease the migration process, we will do that
one sub-architecture at a time, which will require us to remove the
compilation of addr-map.c one sub-architecture at a time.

Therefore, we split the unconditional obj-y inclusion of addr-map.c
into 5 conditionals obj-$(CONFIG_...) lines, one per sub-architecture.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>