pico-imx7d: Add Falcon mode support

Falcon mode boots the kernel directly from SPL, without loading
the full U-Boot.

As pico-imx7d does not have a GPIO for selecting Falcon versus
normal mode, enter in Falcon mode when the customer selects
the CONFIG_SPL_OS_BOOT option in menuconfig.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
diff --git a/configs/pico-imx7d_defconfig b/configs/pico-imx7d_defconfig
index 3eb26c7..6ea49fd 100644
--- a/configs/pico-imx7d_defconfig
+++ b/configs/pico-imx7d_defconfig
@@ -21,6 +21,8 @@
 CONFIG_CMD_BOOTMENU=y
 # CONFIG_CMD_IMI is not set
 # CONFIG_CMD_XIMG is not set
+CONFIG_CMD_SPL=y
+CONFIG_CMD_SPL_WRITE_SIZE=0x20000
 CONFIG_CMD_DFU=y
 CONFIG_CMD_GPIO=y
 CONFIG_CMD_GPT=y