mips/PCI: convert to pci_scan_root_bus() for correct root bus resources

mips/PCI: convert to pci_scan_root_bus() for correct root bus resources

Convert from pci_scan_bus() to pci_scan_root_bus() and remove root bus
resource fixups.  This fixes the problem of "early" and "header" quirks
seeing incorrect root bus resources.

Based on original patch by Deng-Cheng Zhu.

Reference: https://lkml.org/lkml/2011/8/26/89
CC: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Deng-Cheng Zhu <dczhu@mips.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>