x86: use defconfigs from x86/configs/*

Daniel Drake <dsd@gentoo.org> reported:

In 2.6.23, if you unpacked a kernel source tarball and then
ran "make menuconfig" you'd be presented with this message:
    # using defaults found in arch/i386/defconfig

and the default options would be set.

The same thing in 2.6.24 does not give you any "using defaults" message, and
the default config options within menuconfig are rather blank (e.g. no PCI
support). You can work around this by explicitly running "make defconfig"
before menuconfig, but it would be nice to have the behaviour the way it was
for 2.6.23 (and the way it still is for other archs).

Fixed by adding a x86 specific defconfig list to Kconfig.

Fixes: http://bugzilla.kernel.org/show_bug.cgi?id=10470


Tested-by:  <dsd@gentoo.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>