stm32mp1: update bootcmd

Clearly separate bootcmd for stm32mp1 board
(bootcmd_stm32mp) and preboot management.
That solve issue for fastboot continue command.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/configs/stm32mp15_trusted_defconfig b/configs/stm32mp15_trusted_defconfig
index 9be7319..1bb3d0d 100644
--- a/configs/stm32mp15_trusted_defconfig
+++ b/configs/stm32mp15_trusted_defconfig
@@ -3,6 +3,7 @@
 CONFIG_SYS_MALLOC_F_LEN=0x2000
 CONFIG_TARGET_STM32MP1=y
 CONFIG_DISTRO_DEFAULTS=y
+CONFIG_BOOTCOMMAND="run bootcmd_stm32mp"
 CONFIG_SYS_PROMPT="STM32MP> "
 # CONFIG_CMD_BOOTD is not set
 # CONFIG_CMD_ELF is not set