pci: Scale MAX_PCI_REGIONS based on CONFIG_NR_DRAM_BANKS

pci: Scale MAX_PCI_REGIONS based on CONFIG_NR_DRAM_BANKS

If a platform defines CONFIG_NR_DRAM_BANKS, each DRAM bank will be added
as a PCI region. The number of MAX_PCI_REGIONS therefore needs to scale
with the number of DRAM banks, otherwise we will end up with too little
space in the hose->regions array to store all system memory regions.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Simon Glass <sjg@chromium.org>