[PATCH] x86: fix acpi compile without CONFIG_ACPI_BUS

The recent acpi boot patch breaks for me: acpi_fadt needs CONFIG_ACPI_BUS.

Signed-off-By: Chris Wedgwood <cw@f00f.org>
Acked-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>