cmd: fastboot: Enable FASTBOOT_FLASH_NAND for SUNXI_NAND devices

Encountered an issue where fastboot can't write to NAND on a CHIP_pro,
the symbol was neither present in the board's config header, nor the
Kconfig, this patch puts it in the Kconfig and defaults on when
SUNXI_NAND is selected.

Signed-off-by: Ben Young <computermouth@crunchbangplusplus.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

cmd/fastboot/Kconfig

@@ -81,6 +81,16 @@ config FASTBOOT_FLASH_MMC_DEV
 	  regarding the non-volatile storage device. Define this to
 	  the eMMC device that fastboot should use to store the image.
 
+config FASTBOOT_FLASH_NAND_DEV
+	int "Define FASTBOOT NAND FLASH default device"
+	depends on FASTBOOT_FLASH && NAND
+	depends on CMD_MTDPARTS
+	default 0 if ARCH_SUNXI && NAND_SUNXI
+	help
+	  The fastboot "flash" command requires additional information
+	  regarding the non-volatile storage device. Define this to
+	  the NAND device that fastboot should use to store the image.
+
 config FASTBOOT_GPT_NAME
 	string "Target name for updating GPT"
 	depends on FASTBOOT_FLASH