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_mcvevk_defconfig b/configs/socfpga_mcvevk_defconfig
index 12817e5..2a2899d 100644
--- a/configs/socfpga_mcvevk_defconfig
+++ b/configs/socfpga_mcvevk_defconfig
@@ -11,7 +11,7 @@
 CONFIG_FIT=y
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyS0,115200"
-# CONFIG_USE_BOOTCOMMAND is not set
+CONFIG_BOOTCOMMAND="run mmc_mmc"
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE=y
 CONFIG_SYS_CONSOLE_ENV_OVERWRITE=y