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/vinco_defconfig b/configs/vinco_defconfig
index fbc2176..025032b 100644
--- a/configs/vinco_defconfig
+++ b/configs/vinco_defconfig
@@ -15,6 +15,8 @@
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyS0,115200 earlyprintk rw root=/dev/mmcblk0p2 rootfstype=ext4 rootwait quiet lpj=1990656"
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="mmc dev 0 0;mmc read ${loadaddr} ${k_offset} ${k_blksize};mmc read ${oftaddr} ${dtb_offset} ${dtb_blksize};bootz ${loadaddr} -  ${oftaddr}"
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_HUSH_PARSER=y