x86/ACPI: don't overwrite FADT

x86/ACPI: don't overwrite FADT

When marking fields invalid for our own purposes, we should do so in our
local copy (so we will notice later on), not in the firmware provided
one (which another entity may want to look at again, e.g. after kexec).
Also mark the function parameter const to notice such issues right away.

Instead use the pointer at the firmware copy for specifying an adjacent
printk()'s arguments. If nothing else this at least reduces the number
of relocations the assembler hasto emit and the linker has to process.

Fixes: 62d1a69a4e9f ("ACPI: support v5 (reduced HW) sleep interface")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>