x86/Voyager: remove KGDB Kconfig quirk

x86/Voyager has this KGDB quirk:

	select HAVE_ARCH_KGDB if !X86_VOYAGER

This is completely pointless - there's nothing in KGDB that cannot work
on Voyager. Remove it.

Signed-off-by: Ingo Molnar <mingo@elte.hu>