arm: socfpga: SoCKit use environment in common header

This removes the default environment from the SoCKit headers
and instead uses the common environment provided in
socfpga_common.h which now uses distro boot.

Change default devicetree name to match devicetree name in
upstream kernel source.

Signed-off-by: Dalon Westergreen <dwesterg@gmail.com>
Acked-by: Marek Vasut <marex@denx.de>

--
Changes in v2:
 - Remove unneeded CONFIG_BOOTFILE
diff --git a/configs/socfpga_sockit_defconfig b/configs/socfpga_sockit_defconfig
index d0c2bda..bf60783 100644
--- a/configs/socfpga_sockit_defconfig
+++ b/configs/socfpga_sockit_defconfig
@@ -4,6 +4,7 @@
 CONFIG_TARGET_SOCFPGA_TERASIC_SOCKIT=y
 CONFIG_SPL_STACK_R_ADDR=0x00800000
 CONFIG_DEFAULT_DEVICE_TREE="socfpga_cyclone5_sockit"
+CONFIG_DEFAULT_FDT_FILE="socfpga_cyclone5_sockit.dtb"
 CONFIG_FIT=y
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE=y