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/qemu-ppce500_defconfig b/configs/qemu-ppce500_defconfig
index 55f6465..f386f52 100644
--- a/configs/qemu-ppce500_defconfig
+++ b/configs/qemu-ppce500_defconfig
@@ -8,6 +8,8 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
 CONFIG_BOOTDELAY=1
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="test -n \"$qemu_kernel_addr\" && bootm $qemu_kernel_addr - $fdtcontroladdr"
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_LAST_STAGE_INIT=y
 CONFIG_HUSH_PARSER=y