[POWERPC] Make isa_mem_base common to 32 and 64 bits

This defines isa_mem_base on both 32 and 64 bits (it used to be 32 bits
only).  This avoids a few ifdef's in later patches and potentially can
allow support for VGA text mode on 64 bits powerpc.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/include/asm-powerpc/io.h b/include/asm-powerpc/io.h
index e44cdfc..7be26f6 100644
--- a/include/asm-powerpc/io.h
+++ b/include/asm-powerpc/io.h
@@ -50,15 +50,16 @@
 #define PCI_DRAM_OFFSET	pci_dram_offset
 #else
 #define _IO_BASE	pci_io_base
-#define _ISA_MEM_BASE	0
+#define _ISA_MEM_BASE	isa_mem_base
 #define PCI_DRAM_OFFSET	0
 #endif
 
 extern unsigned long isa_io_base;
-extern unsigned long isa_mem_base;
 extern unsigned long pci_io_base;
 extern unsigned long pci_dram_offset;
 
+extern resource_size_t isa_mem_base;
+
 #if defined(CONFIG_PPC32) && defined(CONFIG_PPC_INDIRECT_IO)
 #error CONFIG_PPC_INDIRECT_IO is not yet supported on 32 bits
 #endif