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/total_compute_defconfig b/configs/total_compute_defconfig
index 7c70eb0..8fafee0 100644
--- a/configs/total_compute_defconfig
+++ b/configs/total_compute_defconfig
@@ -15,7 +15,7 @@
 CONFIG_FIT_SIGNATURE=y
 CONFIG_LEGACY_IMAGE_FORMAT=y
 CONFIG_BOOTDELAY=5
-# CONFIG_USE_BOOTCOMMAND is not set
+CONFIG_BOOTCOMMAND="if part number mmc 0 vbmeta is_avb; then  echo MMC with vbmeta partition detected.;  echo starting Android Verified boot.;  avb init 0;   if avb verify; then     set bootargs $bootargs $avb_bootargs;     part start mmc 0 boot boot_start;     part size mmc 0 boot boot_size;     mmc read ${load_addr} ${boot_start} ${boot_size};     bootm ${load_addr} ${load_addr} ${fdt_addr_r};   else;     echo AVB verification failed.;     exit;   fi; elif part number mmc 0 system is_non_avb_android; then   booti ${kernel_addr_r} ${initrd_addr_r} ${fdt_addr_r};else;  echo Booting FIT image.;  bootm ${load_addr} ${load_addr} ${fdt_addr_r}; fi;"
 # CONFIG_DISPLAY_CPUINFO is not set
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_AVB_VERIFY=y