rockchip: timer: add compatible strings for rk3188 and rk3288

The DM driver for ockchip timer blocks is also applicable to the
RK3188 and RK3288 timer blocks: add 'rockchip,rk3188-timer' and
'rockchip,rk3288-timer' to its compatible list to support devices
claiming compatibility with these.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
diff --git a/drivers/timer/rockchip_timer.c b/drivers/timer/rockchip_timer.c
index 07d1448..b847bc4 100644
--- a/drivers/timer/rockchip_timer.c
+++ b/drivers/timer/rockchip_timer.c
@@ -152,6 +152,8 @@
 };
 
 static const struct udevice_id rockchip_timer_ids[] = {
+	{ .compatible = "rockchip,rk3188-timer" },
+	{ .compatible = "rockchip,rk3288-timer" },
 	{ .compatible = "rockchip,rk3368-timer" },
 	{}
 };