arm: imx8m: add OP-TEE node

Add tee node in SoC u-boot device trees. Use a kconfig entry to specify
load and entry addresses for the op-tee image in the respective
defconfig.
Default IMX8M_OPTEE_LOAD_ADDR is supplied. To keep it simple, the same
addresses are used for each SoC as are defined in upstream tf-a
(BL32_BASE) [1].

[1] https://github.com/ARM-software/arm-trusted-firmware/tree/master/plat/imx/imx8m

Signed-off-by: Yannic Moog <y.moog@phytec.de>
diff --git a/arch/arm/mach-imx/imx8m/Kconfig b/arch/arm/mach-imx/imx8m/Kconfig
index 76a8be7..0fe9c46 100644
--- a/arch/arm/mach-imx/imx8m/Kconfig
+++ b/arch/arm/mach-imx/imx8m/Kconfig
@@ -37,6 +37,17 @@
 	  If enabled, please also define the value for ARMV8_SECURE_BASE,
 	  for i.MX8M, it could be some address in OCRAM.
 
+config IMX8M_OPTEE_LOAD_ADDR
+	hex "Load address of OPTEE image"
+	default 0xbe000000 if IMX8MM
+	default 0xbe000000 if IMX8MN
+	default 0x56000000 if IMX8MP
+	default 0xfe000000 if IMX8MQ
+	help
+	  The load and entry address for the OPTEE image. This value defaults to
+	  the one defined in tf-a if not provided in the board defconfig file.
+
+
 choice
 	prompt "NXP i.MX8M board select"
 	optional