ARM: dts: imx8mm-verdin: prepare for dek blob encapsulation

ARM: dts: imx8mm-verdin: prepare for dek blob encapsulation

Prepare for DEK blob encapsulation support through "dek_blob" command.
On ARMv8, u-boot runs in non-secure, thus cannot encapsulate a DEK blob
for encrypted boot.
The DEK blob is encapsulated by OP-TEE through a trusted application
call. U-boot sends and receives the DEK and the DEK blob binaries
through OP-TEE dynamic shared memory.

To enable the DEK blob encapsulation, add to the defconfig:
CONFIG_SECURE_BOOT=y
CONFIG_FAT_WRITE=y
CONFIG_CMD_DEKBLOB=y

Taken from NXP's commit 56d2050f4028 ("imx8m: Add DEK blob encapsulation
for imx8m").

Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>