timer: vt8500: Move timer code to drivers/clocksource

This patch moves arch-vt8500/timer.c into drivers/clocksource and
updates the necessary Kconfig/Makefile options.

Signed-off-by: Tony Prisk <linux@prisktech.co.nz>
diff --git a/arch/arm/mach-vt8500/Kconfig b/arch/arm/mach-vt8500/Kconfig
index 2ed0b7d..570a801 100644
--- a/arch/arm/mach-vt8500/Kconfig
+++ b/arch/arm/mach-vt8500/Kconfig
@@ -8,5 +8,6 @@
 	select GENERIC_CLOCKEVENTS
 	select GENERIC_GPIO
 	select HAVE_CLK
+	select VT8500_TIMER
 	help
 	  Support for VIA/WonderMedia VT8500/WM85xx System-on-Chip.