x86/Voyager: remove X86_BIOS_REBOOT Kconfig quirk

Voyager has this Kconfig quirk:

config X86_BIOS_REBOOT
	bool
	depends on !X86_VOYAGER
	default y

Voyager should use the existing machine_ops.emergency_restart reboot
quirk mechanism instead of a build-time quirk.

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