MIPS: Alchemy: Redo PCI as platform driver

- Rewrite Alchemy PCI support as a platform driver.
- Fixup boards which have PCI.

Run-tested on DB1500 and DB1550.

Signed-off-by: Manuel Lauss <manuel.lauss@googlemail.com>
To: Linux-MIPS <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/2706/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
 delete mode 100644 arch/mips/alchemy/common/pci.c
 delete mode 100644 arch/mips/pci/fixup-au1000.c
 delete mode 100644 arch/mips/pci/ops-au1000.c
 create mode 100644 arch/mips/pci/pci-alchemy.c