pico-imx7d: Enable auxiliary code support

This enables the "bootaux" command so a firmware can be loaded inside
the M4 MCU.
Signed-off-by: NOtavio Salvador <otavio@ossystems.com.br>

configs/pico-imx7d_defconfig

@@ -11,6 +11,7 @@ CONFIG_SPL=y
 CONFIG_SPL_LIBDISK_SUPPORT=y
 CONFIG_ARMV7_BOOT_SEC_DEFAULT=y
 CONFIG_IMX_RDC=y
+CONFIG_IMX_BOOTAUX=y
 CONFIG_DISTRO_DEFAULTS=y
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=arch/arm/mach-imx/spl_sd.cfg"
 CONFIG_BOOTCOMMAND="run findfdt; run finduuid; run distro_bootcmd"