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_defconfig b/configs/xilinx_versal_mini_defconfig
index 03e145f..c90899b 100644
--- a/configs/xilinx_versal_mini_defconfig
+++ b/configs/xilinx_versal_mini_defconfig
@@ -16,6 +16,8 @@
 CONFIG_SYS_LOAD_ADDR=0x8000000
 # CONFIG_LEGACY_IMAGE_FORMAT is not set
 # 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