arm: plat-orion: introduce PLAT_ORION_LEGACY hidden config option

arm: plat-orion: introduce PLAT_ORION_LEGACY hidden config option

Until now, the PLAT_ORION configuration option was common to all the
Marvell EBU SoCs, and selecting this option had the effect of enabling
the MPP code, GPIO code, address decoding and PCIe code from
plat-orion, as well as providing access to driver-specific header
files from plat-orion/include.

However, the Armada 370 and XP SoCs will not use the MPP and GPIO code
(instead some proper pinctrl and gpio drivers are in preparation), and
generally, we want to move away from plat-orion and instead have
everything in mach-mvebu.

That said, in the mean time, we want to leverage the driver-specific
headers as well as the address decoding code, so we introduce
PLAT_ORION_LEGACY. The older Marvell SoCs need to select
PLAT_ORION_LEGACY, while the newer Marvell SoCs need to select
PLAT_ORION. Of course, when PLAT_ORION_LEGACY is selected, it
automatically selects PLAT_ORION.

Then, with just PLAT_ORION, you have the address decoding code plus
the driver-specific headers. If you add PLAT_ORION_LEGACY to this, you
gain the old MPP, GPIO and PCIe code.

Again, this is only a temporary solution until we make all Marvell EBU
platforms converge into the mach-mvebu directory. This solution avoids
duplicating the existing address decoding code into mach-mvebu.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>