ARM: imx: Enable DFU SF on all i.MX6 DHSOM and include dfu_alt_info in env

Enable DFU SF on all i.MX6 DHSOM so the SPI NOR can be exposed via
DFU, and include dfu_alt_info which exposes the full SPI NOR via DFU.
To install new bootloader into the SPI NOR using DFU, it is necessary
to pad the u-boot-with-spl.imx to 0x400 Bytes offset first and then
send it to the board as follows:

"
u-boot=> dfu 0 sf
"

"
host$ dd if=/dev/zero of=pad.bin bs=1024 count=1
host$ cat pad.bin u-boot-with-spl.imx > flash.bin
host$ dfu-util -w -a 0 -D flash.bin
"

Signed-off-by: Marek Vasut <marek.vasut@mailbox.org>

configs/dh_imx6.config

@@ -60,6 +60,7 @@ CONFIG_MISC=y
 
 CONFIG_PINCTRL_IMX6=y
 
+CONFIG_DFU_SF=y
 CONFIG_SDP_LOADADDR=0x17ffffc0
 CONFIG_SPL_FIT=y
 CONFIG_SPL_SPI=y

include/configs/dh_imx6.h

@@ -38,6 +38,7 @@
 #define CFG_EXTRA_ENV_SETTINGS	\
 	"bootm_size=0x10000000\0"	\
 	"console=ttymxc0,115200\0"	\
+	"dfu_alt_info=sf 0:0=flash-bin raw 0 0x200000\0"	\
 	"fdt_addr=0x18000000\0"		\
 	"kernel_addr_r=0x10008000\0"	\
 	"fdt_addr_r=0x13000000\0"	\