x86/Kconfig: Simplify X86_IO_APIC dependencies

Since dependencies are transitive, we don't really need to
repeat those of X86_UP_IOAPIC.

Furthermore avoid the symbol getting entered into .config when
it is off by having the default simply Y and the dependencies
solely handled via the intended for that purpose "depends on".

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Link: http://lkml.kernel.org/r/54D39BC9020000780005D688@mail.emea.novell.com


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