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/sniper_defconfig b/configs/sniper_defconfig
index 354f290..5b03088 100644
--- a/configs/sniper_defconfig
+++ b/configs/sniper_defconfig
@@ -8,7 +8,7 @@
 CONFIG_TARGET_SNIPER=y
 CONFIG_SPL=y
 CONFIG_DISTRO_DEFAULTS=y
-# CONFIG_USE_BOOTCOMMAND is not set
+CONFIG_BOOTCOMMAND="setenv boot_mmc_part ${kernel_mmc_part}; if test reboot-${reboot-mode} = reboot-r; then echo recovery; setenv boot_mmc_part ${recovery_mmc_part}; fi; if test reboot-${reboot-mode} = reboot-b; then echo fastboot; fastboot 0; fi; part start mmc ${boot_mmc_dev} ${boot_mmc_part} boot_mmc_start; part size mmc ${boot_mmc_dev} ${boot_mmc_part} boot_mmc_size; mmc dev ${boot_mmc_dev}; mmc read ${kernel_addr_r} ${boot_mmc_start} ${boot_mmc_size} && bootm ${kernel_addr_r};"
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 # CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_USE_SECTOR is not set
 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_USE_PARTITION=y