stm32mp: configs: activate the command stm32key only for ST boards

This command is used to evaluate the secure boot on stm32mp SOC,
it is deactivated by default in real products.

We activate this command only in STMicroelectronics defconfig
used with the evaluation boards.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
diff --git a/arch/arm/mach-stm32mp/Kconfig b/arch/arm/mach-stm32mp/Kconfig
index 7c25266..0e59931 100644
--- a/arch/arm/mach-stm32mp/Kconfig
+++ b/arch/arm/mach-stm32mp/Kconfig
@@ -174,10 +174,12 @@
 
 config CMD_STM32KEY
 	bool "command stm32key to fuse public key hash"
-	default y
+	default n
 	help
 		fuse public key hash in corresponding fuse used to authenticate
 		binary.
+		This command is used to evaluate the secure boot on stm32mp SOC,
+		it is deactivated by default in real products.
 
 config PRE_CON_BUF_ADDR
 	default 0xC02FF000