x86/dmi: fix dmi_alloc() section mismatches

Impact: section mismatch fix

Ingo reports these warnings:
> WARNING: vmlinux.o(.text+0x6a288e): Section mismatch in reference from
> the function dmi_alloc() to the function .init.text:extend_brk()
> The function dmi_alloc() references
> the function __init extend_brk().
> This is often because dmi_alloc lacks a __init annotation or the
> annotation of extend_brk is wrong.

dmi_alloc() is a static inline, and so should be immune to this
kind of error.  But force it to be inlined and make it __init
anyway, just to be extra sure.

All of dmi_alloc()'s callers are already __init.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <49C6B23C.2040308@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>