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/P2041RDB_SDCARD_defconfig b/configs/P2041RDB_SDCARD_defconfig
index eb97360..253af71 100644
--- a/configs/P2041RDB_SDCARD_defconfig
+++ b/configs/P2041RDB_SDCARD_defconfig
@@ -16,6 +16,8 @@
 CONFIG_SYS_FSL_PBL_PBI="board/freescale/corenet_ds/pbi.cfg"
 CONFIG_SYS_FSL_PBL_RCW="board/freescale/corenet_ds/rcw_p2041rdb.cfg"
 CONFIG_BOOTDELAY=10
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="setenv bootargs root=/dev/$bdev rw console=$consoledev,$baudrate $othbootargs;tftp $loadaddr $bootfile;tftp $fdtaddr $fdtfile;bootm $loadaddr - $fdtaddr"
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_BOARD_EARLY_INIT_R=y
 CONFIG_ID_EEPROM=y