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/ge_bx50v3_defconfig b/configs/ge_bx50v3_defconfig
index 21cb0f3..8cfe772 100644
--- a/configs/ge_bx50v3_defconfig
+++ b/configs/ge_bx50v3_defconfig
@@ -15,6 +15,8 @@
 CONFIG_SUPPORT_RAW_INITRD=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_BOOTDELAY=1
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="run doquiet; run tryboot"
 CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE=y
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_DISPLAY_BOARDINFO_LATE=y