arm: zynq: Move bootcommand to defconfig

It will cleanup generic config and enable option to change it for every
board.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/configs/zynq_zybo_defconfig b/configs/zynq_zybo_defconfig
index a25a750..1dc2924 100644
--- a/configs/zynq_zybo_defconfig
+++ b/configs/zynq_zybo_defconfig
@@ -8,6 +8,8 @@
 CONFIG_FIT=y
 CONFIG_FIT_SIGNATURE=y
 CONFIG_FIT_VERBOSE=y
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="run $modeboot || run distro_bootcmd"
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_SPL=y
 CONFIG_SPL_STACK_R=y