ARM: ixp4xx: fix building both pci drivers

ARM: ixp4xx: fix building both pci drivers

When both the old and the new PCI drivers are enabled
in the same kernel, there are a couple of namespace
conflicts that cause a build failure:

drivers/pci/controller/pci-ixp4xx.c:38: error: "IXP4XX_PCI_CSR" redefined [-Werror]
   38 | #define IXP4XX_PCI_CSR                  0x1c
      |
In file included from arch/arm/mach-ixp4xx/include/mach/hardware.h:23,
                 from arch/arm/mach-ixp4xx/include/mach/io.h:15,
                 from arch/arm/include/asm/io.h:198,
                 from include/linux/io.h:13,
                 from drivers/pci/controller/pci-ixp4xx.c:20:
arch/arm/mach-ixp4xx/include/mach/ixp4xx-regs.h:221: note: this is the location of the previous definition
  221 | #define IXP4XX_PCI_CSR(x) ((volatile u32 *)(IXP4XX_PCI_CFG_BASE_VIRT+(x)))
      |
drivers/pci/controller/pci-ixp4xx.c:148:12: error: 'ixp4xx_pci_read' redeclared as different kind of symbol
  148 | static int ixp4xx_pci_read(struct ixp4xx_pci *p, u32 addr, u32 cmd, u32 *data)
      |            ^~~~~~~~~~~~~~~

Rename both the ixp4xx_pci_read/ixp4xx_pci_write functions and the
IXP4XX_PCI_CSR macro. In each case, I went with the version that
has fewer callers to keep the change small.

Fixes: f7821b493458 ("PCI: ixp4xx: Add a new driver for IXP4xx")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: soc@kernel.org
Link: https://lore.kernel.org/r/20210721151546.2325937-1-arnd@kernel.org'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>