[x86-tip] RSDP changes converted i4790 box SMP -> UP

[Mike Galbraith]

Hi Juergen,

Yesterday I wanted to test the RETPOLINE stuff in tip and tip-rt, but
discovered instead that my box had turned into a complete slug, not due
to incredible RETPOLINE overhead, rather because box had forgotten that
it had more than one CPU.  I was going to leave it for the weekend, but
firing up gitk over morning java, I noticed the commits below, and sure
enough, that's what broke my box.  Given other people's boxen work,
seems likely that the authors of the AMI BIOS in this box were a bit
more creative than usual.

commit 9ede5d5e672586e016eadd5c0aedb6f12e660029 (HEAD -> x86-tip)
Author: Mike Galbraith <mgalbraith@xxxxxxx>
Date:   Fri Jan 12 04:17:52 2018 +0100

    Revert "x86/boot: Add the ACPI RSDP address to struct setup_header::acpi_rdsp_addr"
    
    This reverts commit 2f74cbf947f45fa082dda8eac1a1f1299a372f49.

commit 0d0b6a9a0d452eaf635580fce8319d49be8b45ed
Author: Mike Galbraith <mgalbraith@xxxxxxx>
Date:   Fri Jan 12 04:17:30 2018 +0100

    Revert "x86/acpi: Take the RSDP address for boot parameters if available"
    
    This reverts commit 0c89cf36424f7c1177de8a5712514d7cc2eb369f.

commit 2e9b091da44e75f16b8bad776f40de83abb637ff (origin/x86-tip)
Merge: 41c34211458c 1ccb8feda747
Author: Ingo Molnar <mingo@xxxxxxxxxx>
Date:   Thu Jan 11 06:54:18 2018 +0100

    Merge branch 'perf/core'