x86/kconfig: Remove redundant 'default n' lines from all x86 Kconfig's

'default n' is the default value for any bool or tristate Kconfig
setting so there is no need to write it explicitly.

Also, since commit:

  f467c564 ("kconfig: only write '# CONFIG_FOO is not set' for visible symbols")

... the Kconfig behavior is the same regardless of 'default n' being present or not:

    ...
    One side effect of (and the main motivation for) this change is making
    the following two definitions behave exactly the same:

        config FOO
                bool

        config FOO
                bool
                default n

    With this change, neither of these will generate a
    '# CONFIG_FOO is not set' line (assuming FOO isn't selected/implied).
    That might make it clearer to people that a bare 'default n' is
    redundant.
    ...

Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Juergen Gross <jgross@suse.co>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/20181016134217eucas1p2102984488b89178a865162553369025b%7EeGpI5NlJo0851008510eucas1p2D@eucas1p2.samsung.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>