Change ACPI to use dev_archdata instead of firmware_data

This patch changes ACPI to use the new dev_archdata on i386, x86_64
and ia64 (is there any other arch using ACPI ?) to store it's
acpi_handle.

It also removes the firmware_data field from struct device as this
was the only user.

Only build-tested on x86

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>