arch/x86: Define HPET_ADDRESS_OVERRIDE

Symbol defined in via/cx700 but also used elsewhere.

Change-Id: I31d6043e71dea474de00f609b9609a628ecc6eb8
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/26510
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>

src/arch/x86/Kconfig

@@ -193,6 +193,9 @@ config IOAPIC_INTERRUPTS_ON_APIC_SERIAL_BUS
 	bool
 	default n
 
+config HPET_ADDRESS_OVERRIDE
+	def_bool n
+
 config HPET_ADDRESS
 	hex
 	default 0xfed00000 if !HPET_ADDRESS_OVERRIDE