PPC: e500 pci host: Add support for ATMUs

PPC: e500 pci host: Add support for ATMUs

The e500 PCI controller has configurable windows that allow a guest OS
to selectively map parts of the PCI bus space to CPU address space and
to selectively map parts of the CPU address space for DMA requests into
PCI visible address ranges.

So far, we've simply assumed that this mapping is 1:1 and ignored it.

However, the PCICSRBAR (CCSR mapped in PCI bus space) always has to live
inside the first 32bits of address space. This means if we always treat
all mappings as 1:1, this map will collide with our RAM map from the CPU's
point of view.

So this patch adds proper ATMU support which allows us to keep the PCICSRBAR
below 32bits local to the PCI bus and have another, different window to PCI
BARs at the upper end of address space. We leverage this on e500plat though,
mpc8544ds stays virtually 1:1 like it was before, but now also goes via ATMU.

With this patch, I can run guests with lots of RAM and not coincidently access
MSI-X mappings while I really want to access RAM.

Signed-off-by: Alexander Graf <[email protected]>