configs: stm32mp1: replace STM32MP1_TRUSTED by TFABOOT

Activate ARCH_SUPPORT_TFABOOT and replace the arch stm32mp
specific config CONFIG_STM32MP1_TRUSTED by the generic CONFIG_TFABOOT
introduced by the commit 535d76a12150 ("armv8: layerscape: Add TFABOOT
support").
This config CONFIG_TFABOOT is activated for the trusted boot chain,
when U-Boot is loaded by TF-A.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index bbb1e27..dd41090 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1586,6 +1586,7 @@
 config ARCH_STM32MP
 	bool "Support STMicroelectronics STM32MP Socs with cortex A"
 	select ARCH_MISC_INIT
+	select ARCH_SUPPORT_TFABOOT
 	select BOARD_LATE_INIT
 	select CLK
 	select DM