clocksource/drivers/oxnas: Add OX820 compatible

In order to support the Oxford Semiconductor OX820 SoC, add new
compatible string to rps timer driver.
Also add new string in the dt-bindings.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
diff --git a/drivers/clocksource/timer-oxnas-rps.c b/drivers/clocksource/timer-oxnas-rps.c
index bd887e2..d630bf4 100644
--- a/drivers/clocksource/timer-oxnas-rps.c
+++ b/drivers/clocksource/timer-oxnas-rps.c
@@ -295,3 +295,5 @@
 
 CLOCKSOURCE_OF_DECLARE(ox810se_rps,
 		       "oxsemi,ox810se-rps-timer", oxnas_rps_timer_init);
+CLOCKSOURCE_OF_DECLARE(ox820_rps,
+		       "oxsemi,ox820se-rps-timer", oxnas_rps_timer_init);