clocksource/drivers/timer-versatile: Clear OF_POPULATED flag

The commit 4f41fe38 ("clocksource/drivers/timer-probe: Avoid
creating dead devices") broke the handling of arm,vexpress-sysreg [1].

The arm,vexpress-sysreg device is handled by both timer-versatile.c and
drivers/mfd/vexpress-sysreg.c. While the timer driver doesn't use the
device, the mfd driver still needs a device to probe.

So, this patch clears the OF_POPULATED flag to continue creating the
device.

[1] - https://lore.kernel.org/lkml/20200324175955.GA16972@arm.com/

Fixes: 4f41fe38 ("clocksource/drivers/timer-probe: Avoid creating dead devices")
Signed-off-by: Saravana Kannan <saravanak@google.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200324195302.203115-1-saravanak@google.com

drivers/clocksource/timer-versatile.c

@@ -6,6 +6,7 @@
 
 #include <linux/clocksource.h>
 #include <linux/io.h>
+#include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/sched_clock.h>
 
@@ -22,6 +23,8 @@ static int __init versatile_sched_clock_init(struct device_node *node)
 {
 	void __iomem *base = of_iomap(node, 0);
 
+	of_node_clear_flag(node, OF_POPULATED);
+
 	if (!base)
 		return -ENXIO;