sunxi: OrangePi Zero 2: Enable SPI booting

The OrangePi Zero 2 board comes with 2MB of SPI flash, from which the
BROM is able to boot from. Please note that the fuse setup requires
PC5 (BOOT_SEL3) to be pulled to GND for that to actually work.

Enable the SPL code responsible for finding and loading U-Boot proper and
friends, so that u-boot-sunxi-with-spl.bin can be written into the flash.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Ivan Shishkin <s45rus@gmail.com>
diff --git a/configs/orangepi_zero2_defconfig b/configs/orangepi_zero2_defconfig
index 54faf6a..ceef51b 100644
--- a/configs/orangepi_zero2_defconfig
+++ b/configs/orangepi_zero2_defconfig
@@ -9,6 +9,7 @@
 CONFIG_MACH_SUN50I_H616=y
 CONFIG_MMC0_CD_PIN="PF6"
 CONFIG_R_I2C_ENABLE=y
+CONFIG_SPL_SPI_SUNXI=y
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
 CONFIG_SPL_I2C=y
 CONFIG_SPL_SYS_I2C_LEGACY=y