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/k2g_evm_defconfig b/configs/k2g_evm_defconfig
index 831ff69..f0a7d83 100644
--- a/configs/k2g_evm_defconfig
+++ b/configs/k2g_evm_defconfig
@@ -21,7 +21,7 @@
 CONFIG_SPL_SPI=y
 CONFIG_DISTRO_DEFAULTS=y
 CONFIG_OF_BOARD_SETUP=y
-# CONFIG_USE_BOOTCOMMAND is not set
+CONFIG_BOOTCOMMAND="run findfdt; run envboot; run init_${boot}; run get_mon_${boot} run_mon; run set_name_pmmc get_pmmc_${boot} run_pmmc; run get_kern_${boot}; run init_fw_rd_${boot}; run get_fdt_${boot}; run run_kern"
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_SPL_I2C=y