ARM: stm32mp: Add stm32mp21 support.

Add "st,stm32mp21-rifsc" compatible for stm32mp21 support.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Change-Id: Ia03235dceb461aa805b7a015e47f72755b8a7159
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/u-boot/+/457869
ACI: CITOOLS <MDG-smet-aci-reviews@list.st.com>

Author: Patrice Chotard

arch/arm/mach-stm32mp/stm32mp2/rifsc.c

@@ -355,6 +355,7 @@ static int stm32_rifsc_remove(struct udevice *bus)
 
 static const struct udevice_id stm32_rifsc_ids[] = {
 	{ .compatible = "st,stm32mp25-rifsc" },
+	{ .compatible = "st,stm32mp21-rifsc" },
 	{},
 };