remoteproc: stm32: use reset for hold boot

Use the reset function to handle the hold boot bit in RCC
with device tree handle with MCU_HOLD_BOOT identifier.

This generic reset allows to remove the two specific properties:
- st,syscfg-holdboot
- st,syscfg-tz

This patch prepares alignment with kernel device tree.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Cc: Fabien DESSENNE <fabien.dessenne@st.com>
Cc: Arnaud POULIQUEN <arnaud.pouliquen@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>
diff --git a/arch/arm/dts/stm32mp15-u-boot.dtsi b/arch/arm/dts/stm32mp15-u-boot.dtsi
index 7ec90fe..d0aa5ea 100644
--- a/arch/arm/dts/stm32mp15-u-boot.dtsi
+++ b/arch/arm/dts/stm32mp15-u-boot.dtsi
@@ -159,6 +159,13 @@
 	u-boot,dm-pre-proper;
 };
 
+/* temp = waiting kernel update */
+&m4_rproc {
+	resets = <&rcc MCU_R>,
+		 <&rcc MCU_HOLD_BOOT_R>;
+	reset-names = "mcu_rst", "hold_boot";
+};
+
 &pinctrl {
 	u-boot,dm-pre-reloc;
 };