pico-imx7d: Enable CONFIG_ARMV7_BOOT_SEC_DEFAULT

Currently the CAAM driver fails to be probed:

caam 30900000.caam: Entropy delay = 3200
caam 30900000.caam: failed to acquire DECO 0
caam 30900000.caam: failed to instantiate RNG

CAAM needs to be initialized in secure world, so enable
CONFIG_ARMV7_BOOT_SEC_DEFAULT to allow the driver to
probe successfully.

Tested with kernel mainline version 4.17.2.
Signed-off-by: NFabio Estevam <festevam@gmail.com>
Signed-off-by: NOtavio Salvador <otavio@ossystems.com.br>

configs/pico-imx7d_defconfig

@@ -9,6 +9,7 @@ CONFIG_SPL_MMC_SUPPORT=y
 CONFIG_SPL_SERIAL_SUPPORT=y
 CONFIG_SPL=y
 CONFIG_SPL_LIBDISK_SUPPORT=y
+CONFIG_ARMV7_BOOT_SEC_DEFAULT=y
 CONFIG_IMX_RDC=y
 CONFIG_DISTRO_DEFAULTS=y
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=arch/arm/mach-imx/spl_sd.cfg"