ACPI: add FW_BUG to OSI(Linux) message

Linux-2.6.22 initiated a dmesg complaint when it saw BIOS that invoked
OSI(Linux).  Linux-2.6.23 continued that complaint and started our
policy of ignoring the bogus BIOS request.

Past-time for Linux to label that complaint with FW_BUG.

Signed-off-by: Len Brown <len.brown@intel.com>