pci: pci-uclass: Dynamically allocate the PCI regions

Instead of using a fixed length pre-allocated array of regions, this
patch moves to dynamically allocating the regions based on the number
of available regions plus the necessary regions for DRAM banks.

Since MAX_PCI_REGIONS is not needed any more, its removed completely
with this patch.

Signed-off-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Cc: Bin Meng <bmeng.cn@gmail.com>
Cc: Thierry Reding <treding@nvidia.com>
Cc: Marek Vasut <marek.vasut+renesas@gmail.com>