ARM: dts: stm32: Update Cortex-M4 reset declarations on stm32mp15

Since the introduction of the SCMI for the management
of the MCU hold boot in OP-TEE, management of the hold boot by SMC call
is deprecated.
- Clean the st,syscfg-tz  which allows to determine if the trust
zone is enable.
- Add reset-names properties to be able to differentiate the MCU reset and
  the MCU HOLD BOOT.
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>

arch/arm/boot/dts/stm32mp151.dtsi

@@ -1823,8 +1823,8 @@ m4_rproc: m4@10000000 {
 			      <0x30000000 0x40000>,
 			      <0x38000000 0x10000>;
 			resets = <&rcc MCU_R>;
+			reset-names = "mcu_rst";
 			st,syscfg-holdboot = <&rcc 0x10C 0x1>;
-			st,syscfg-tz = <&rcc 0x000 0x1>;
 			st,syscfg-pdds = <&pwr_mcu 0x0 0x1>;
 			st,syscfg-rsc-tbl = <&tamp 0x144 0xFFFFFFFF>;
 			st,syscfg-m4-state = <&tamp 0x148 0xFFFFFFFF>;