Convert CONFIG_USE_BOOTCOMMAND et al to Kconfig

This converts the following to Kconfig:
   CONFIG_USE_BOOTCOMMAND
   CONFIG_BOOTCOMMAND
   CONFIG_RAMBOOTCOMMAND
   CONFIG_NFSBOOTCOMMAND

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/xilinx_versal_mini_emmc0_defconfig b/configs/xilinx_versal_mini_emmc0_defconfig
index 9c848e9..c897339 100644
--- a/configs/xilinx_versal_mini_emmc0_defconfig
+++ b/configs/xilinx_versal_mini_emmc0_defconfig
@@ -12,6 +12,8 @@
 # CONFIG_EXPERT is not set
 CONFIG_SYS_LOAD_ADDR=0x8000000
 # CONFIG_AUTOBOOT is not set
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="run distro_bootcmd"
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_BOARD_EARLY_INIT_R=y