KConfig: Vexpress: build the ARM_GLOBAL_TIMER with vexpress platform

The Cortex A5 now contains bindings for the global timer
driver. Ensure that the driver is built with a vexpress platform.
Signed-off-by: Matthew Leach <matthew.leach@arm.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

arch/arm/mach-vexpress/Kconfig

@@ -4,6 +4,7 @@ config ARCH_VEXPRESS
 	select ARCH_SUPPORTS_BIG_ENDIAN
 	select ARM_AMBA
 	select ARM_GIC
+	select ARM_GLOBAL_TIMER
 	select ARM_TIMER_SP804
 	select COMMON_CLK_VERSATILE
 	select HAVE_ARM_SCU if SMP