[PATCH] mem driver: fix conditional on isa i/o support

This change corrects the logic on the preprocessor conditionals that
include support for ISA port i/o (/dev/ioports) into the mem character
driver.

This fixes the following error when building for powerpc platforms with
CONFIG_PCI=n.

  drivers/built-in.o: undefined reference to `pci_io_base'

Signed-off-by: Geoff Levand <geoffrey.levand@am.sony.com>
Acked-by: Linas Vepstas <lins@austin.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>