dt-bindings: clock: imx8mn: add SNVS clock

Add macro for the SNVS clock of the i.MX8MN.
Signed-off-by: Horia Geantă <horia.geanta@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

include/dt-bindings/clock/imx8mn-clock.h

@@ -228,6 +228,8 @@
 #define IMX8MN_SYS_PLL2_333M_CG			209
 #define IMX8MN_SYS_PLL2_500M_CG			210
 
-#define IMX8MN_CLK_END				211
+#define IMX8MN_CLK_SNVS_ROOT			211
+
+#define IMX8MN_CLK_END				212
 
 #endif