Orion: make PCIe/PCI support use mbus DRAM info

Make the Orion PCIe/PCI code initialise MBUS decode windows based on
mbus_dram_target_info instead of reading the info from the Orion DDR
unit decode registers directly, and move the window code with the other
PCI code, where it can be called as part of the generic PCIe/PCI init
process.

Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Reviewed-by: Tzachi Perelstein <tzachi@marvell.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Nicolas Pitre <nico@marvell.com>