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/topic_miamiplus_defconfig b/configs/topic_miamiplus_defconfig
index 03d1887..763bd8c 100644
--- a/configs/topic_miamiplus_defconfig
+++ b/configs/topic_miamiplus_defconfig
@@ -78,3 +78,4 @@
 CONFIG_CI_UDC=y
 CONFIG_USB_GADGET_DOWNLOAD=y
 CONFIG_USB_FUNCTION_THOR=y
+CONFIG_SYS_TIMER_COUNTS_DOWN=y