feat(plat/arm/rdfremont): Add a new property for PCIe in FDT

Add a new property for PCIe region information.

The property is formatted as follows
struct pcie_rootport_mmio_mmap {
	uint64_t ecam1.start;
	uint64_t ecam1.size;
	uint64_t mmiol.start;
	uint64_t mmiol.size;
	uint64_t mmioh.start;
	uint64_t mmioh.size;
	uint64_t bus.start;
	uint64_t bus.size;
	uint64_t base_interrupt_id;
};

struct pcie_rootbridge_config {
	struct pcie_rootport_mmio_mmap mmap[number of rp];
	uint64_t segment;
	uint64_t hostbridge_id;
	uint64_t translation;
};

The property region is pre-initialized to allocate a region equivalent
to the sizeof(struct pcie_ecam_mmio_mmap) * (number of PCIE RPs)

Signed-off-by: Nishant Sharma <nishant.sharma@arm.com>