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/integratorcp_cm926ejs_defconfig b/configs/integratorcp_cm926ejs_defconfig
index 12004f1..3d15887 100644
--- a/configs/integratorcp_cm926ejs_defconfig
+++ b/configs/integratorcp_cm926ejs_defconfig
@@ -10,6 +10,8 @@
 CONFIG_SYS_LOAD_ADDR=0x7fc0
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="root=/dev/mtdblock0 console=ttyAMA0 console=tty ip=dhcp netdev=27,0,0xfc800000,0xfc800010,eth0 video=clcdfb:0"
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="tftpboot ; bootm"
 # CONFIG_DISPLAY_CPUINFO is not set
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_MISC_INIT_R=y