stm32mp: handle SYSRESET

Add support of sysreset with generic driver "syscon-reboot"
provided by RCC, for U-boot and for SPL.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 777b2f0..190f883 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1166,6 +1166,7 @@
 	select REGMAP
 	select SUPPORT_SPL
 	select SYSCON
+	select SYSRESET
 	select SYS_THUMB_BUILD
 	help
 	  Support for STM32MP SoC family developed by STMicroelectronics,