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/socfpga_dbm_soc1_defconfig b/configs/socfpga_dbm_soc1_defconfig
index 78b7cc7..baae2f2 100644
--- a/configs/socfpga_dbm_soc1_defconfig
+++ b/configs/socfpga_dbm_soc1_defconfig
@@ -10,6 +10,8 @@
 CONFIG_FIT=y
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyS0,115200"
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="run mmc_mmc"
 CONFIG_USE_PREBOOT=y
 CONFIG_PREBOOT="run try_bootscript"
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y