[PATCH] Note on ACPI build fix

Even after the previous fix you can still set CONFIG_ACPI_BOOT
indirectly even without CONFIG_ACPI by choosing CONFIG_PCI and
CONFIG_PCI_MMCONFIG.

That doesn't build very well either.

This makes PCI_MMCONFIG depend on ACPI, fixing that hole.

[ I guess in theory Kconfig could follow the whole chain of dependencies
  for things that get selected, but that sounds insanely complicated, so
  we'll just fix up these things by hand.  --Linus ]

Signed-off-by: Alexander Nyberg <alexn@telia.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>