ia64: Fix kernel BUG at lib/ioremap.c:72!

Commit 0bbf47ea ("ia64: use asm-generic/io.h") results in a BUG
while booting ia64.  This is because asm-generic/io.h defines
PCI_IOBASE, which results in the function acpi_pci_root_remap_iospace()
doing a lot of unnecessary (and wrong) things.

I'd suggested an #if !CONFIG_IA64 in the functon, but Arnd suggested
keeping the fix inside the arch/ia64 tree.

Fixes: 0bbf47ea ("ia64: use asm-generic/io.h")
Suggested-by: Arnd Bergman <arnd@arndb.de>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>