board: lsxl: use CONFIG_DEFAULT_FDT_FILE

Drop our own CONFIG_FDTFILE handling in favor of the generic
CONFIG_DEFAULT_FDT_FILE one.

Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/configs/lsxhl_defconfig b/configs/lsxhl_defconfig
index 33bec60..8f0672b 100644
--- a/configs/lsxhl_defconfig
+++ b/configs/lsxhl_defconfig
@@ -26,6 +26,7 @@
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyS0,115200 root=/dev/sda2"
 CONFIG_BOOTCOMMAND="run bootcmd_${bootsource}"
+CONFIG_DEFAULT_FDT_FILE="kirkwood-lsxhl.dtb"
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 # CONFIG_DISPLAY_BOARDINFO is not set