CONFIG_X86_ES7000=y, CONFIG_X86_GENERICARCH=n, CONFIG_ACPI=y build broken

[Roland Dreier <rdreier@cisco.com>]

(sending to Vivek since he seems to be one of the last people to touch
this code)

For some strange reason I found myself compiling a kernel with
CONFIG_X86_ES7000 and CONFIG_ACPI set and CONFIG_X86_GENERICARCH not
set.  It died with

    arch/i386/kernel/built-in.o: In function `acpi_parse_madt':
    boot.c:(.init.text+0x68b7): undefined reference to `acpi_madt_oem_check'
    arch/i386/kernel/built-in.o: In function `get_smp_config':
    (.init.text+0x9f98): undefined reference to `mps_oem_check'
    arch/i386/kernel/built-in.o: In function `connect_bsp_APIC':
    (.init.text+0xa340): undefined reference to `enable_apic_mode'
    arch/i386/kernel/built-in.o: In function `connect_bsp_APIC':
    (.init.text+0xa370): undefined reference to `enable_apic_mode'

this seems to be because eg acpi_madt_oem_check() and mps_oem_check()
are defined in arch/i386/mach-generic/es7000.c, but arch/i386/Makefile
only goes into mach-generic if CONFIG_X86_GENERICARCH is set.
I didn't track down why enable_apic_mode is broken yet.

No patch because I don't understand how this subarch stuff is supposed
to build :(

 - R.