stm32mp1: add trusted boot with TF-A

Add support of trusted boot, using TF-A as first stage bootloader,
The boot sequence is
  BootRom >=> TF-A.stm32 (clock & DDR) >=> U-Boot.stm32

The TF-A monitor provides secure monitor with support of SMC
- proprietary to manage secure devices (BSEC for example)
- PSCI for power

The same device tree is used for STMicroelectronics boards with
basic boot and with trusted boot.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/board/st/stm32mp1/MAINTAINERS b/board/st/stm32mp1/MAINTAINERS
index 48d8fd2..0a2eddb 100644
--- a/board/st/stm32mp1/MAINTAINERS
+++ b/board/st/stm32mp1/MAINTAINERS
@@ -2,7 +2,8 @@
 M:	Patrick Delaunay <patrick.delaunay@st.com>
 L:	uboot-stm32@st-md-mailman.stormreply.com (moderated for non-subscribers)
 S:	Maintained
+F:	arch/arm/dts/stm32mp157*
 F:	board/st/stm32mp1
-F:	include/configs/stm32mp1.h
 F:	configs/stm32mp15_basic_defconfig
-F:	arch/arm/dts/stm32mp157*
+F:	configs/stm32mp15_trusted_defconfig
+F:	include/configs/stm32mp1.h