stm32mp1: configs: activate CONFIG_SILENT_CONSOLE

Allow to disable console with environment variable 'silent':
> env set silent 1; env save

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/arch/arm/mach-stm32mp/Kconfig b/arch/arm/mach-stm32mp/Kconfig
index 9dc3c4d..e5f05af 100644
--- a/arch/arm/mach-stm32mp/Kconfig
+++ b/arch/arm/mach-stm32mp/Kconfig
@@ -47,6 +47,7 @@
 	imply BOOTSTAGE
 	imply CMD_BOOTCOUNT
 	imply CMD_BOOTSTAGE
+	imply SILENT_CONSOLE
 	imply SYSRESET_PSCI if STM32MP1_TRUSTED
 	imply SYSRESET_SYSCON if !STM32MP1_TRUSTED
 	help