[MIPS] Alchemy: Fix PCI-memory access

The problem was introduced in 2.6.18.3 with the casting of some
36bit-defines (PCI memory) in au1000.h to resource_size_t which may be
u32 or u64 depending on the experimental CONFIG_RESOURCES_64BIT.

With unset CONFIG_RESOURCES_64BIT, the pci-memory cannot be accessed
because the ioremap in arch/mips/au1000/common/pci.c already used the
truncated addresses.
With set CONFIG_RESOURCES_64BIT, things get even worse, because PCI-scan
aborts, due to resource conflict: request_resource() in arch/mips/pci/pci.c
fails because the maximum iomem-address is 0xffffffff (32bit) but the
pci-memory-start-address is 0x440000000 (36bit).

To get pci working again, I propose the following patch:

1. remove the resource_size_t-casting from au1000.h again
2. make the casting in arch/mips/au1000/common/pci.c (it's allowed and
necessary here. The 36bit-handling will be done in __fixup_bigphys_addr).

With this patch pci works again like in 2.6.18.2, the gcc-compile warnings
in pci.c are gone and it doesn't depend on CONFIG_EXPERIMENTAL.

Signed-off-by: Alexander Bigga <ab@mycable.de>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>