boards: Enable IPM driver on colibri_imx7d_m4 board

This board enables the IPM driver on on colibri_imx7d_m4 board.

Signed-off-by: Diego Sueiro <diego.sueiro@gmail.com>
diff --git a/boards/arm/colibri_imx7d_m4/colibri_imx7d_m4.dts b/boards/arm/colibri_imx7d_m4/colibri_imx7d_m4.dts
index e1ff769..509dea2 100644
--- a/boards/arm/colibri_imx7d_m4/colibri_imx7d_m4.dts
+++ b/boards/arm/colibri_imx7d_m4/colibri_imx7d_m4.dts
@@ -20,6 +20,7 @@
 		sw0    = &user_switch_1;
 		i2c-4  = &i2c4;
 		pwm-1  = &pwm1;
+		mu-b   = &mub;
 	};
 
 	chosen {
@@ -68,3 +69,7 @@
 &pwm1 {
 	status = "ok";
 };
+
+&mub {
+	status = "ok";
+};