dt-bindings: clock: imx8mm: Add SNVS clock

Add macro for the SNVS clock of the i.MX8MM.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

include/dt-bindings/clock/imx8mm-clock.h

@@ -245,6 +245,8 @@
 #define IMX8MM_CLK_GPIO4_ROOT			226
 #define IMX8MM_CLK_GPIO5_ROOT			227
 
-#define IMX8MM_CLK_END				228
+#define IMX8MM_CLK_SNVS_ROOT			228
+
+#define IMX8MM_CLK_END				229
 
 #endif