sunxi: Correct typo CONFIG_FTDFILE => CONFIG_FDTFILE

Patch is the result of:
  sed -i -e 's/FTDFILE/FDTFILE/g' board/sunxi/Kconfig configs/* include/configs/sunxi-common.h
  sed -i -e 's/ftdfile/fdtfile/g' board/sunxi/Kconfig

Reported-by: Vagrant Cascadian <vagrant@debian.org>
Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Acked-by: Hans de Goede <hdegoede@redhat.com>
[ ijc -- s/Spotted-by/Reported-by/ and resolve conflict vs "remove
         redundant "SPL" from CONFIG_SYS_EXTRA_OPTIONS" ]
diff --git a/configs/Cubieboard2_FEL_defconfig b/configs/Cubieboard2_FEL_defconfig
index ae5e25a..353b04a 100644
--- a/configs/Cubieboard2_FEL_defconfig
+++ b/configs/Cubieboard2_FEL_defconfig
@@ -1,5 +1,5 @@
 CONFIG_SPL=y
 CONFIG_SYS_EXTRA_OPTIONS="CUBIEBOARD2,SPL_FEL,AXP209_POWER,SUNXI_GMAC,AHCI,SATAPWR=SUNXI_GPB(8),USB_EHCI"
-CONFIG_FTDFILE="sun7i-a20-cubieboard2.dtb"
+CONFIG_FDTFILE="sun7i-a20-cubieboard2.dtb"
 +S:CONFIG_ARM=y
 +S:CONFIG_TARGET_SUN7I=y