Convert CONFIG_SYS_TIMER_COUNTS_DOWN to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_TIMER_COUNTS_DOWN

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/vexpress_ca9x4_defconfig b/configs/vexpress_ca9x4_defconfig
index 234686e..70ce13e 100644
--- a/configs/vexpress_ca9x4_defconfig
+++ b/configs/vexpress_ca9x4_defconfig
@@ -54,3 +54,4 @@
 CONFIG_SMC911X_32_BIT=y
 CONFIG_BAUDRATE=38400
 CONFIG_CONS_INDEX=0
+CONFIG_SYS_TIMER_COUNTS_DOWN=y