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/sama5d27_wlsom1_ek_qspiflash_defconfig b/configs/sama5d27_wlsom1_ek_qspiflash_defconfig
index 42ebb1a..c23c209 100644
--- a/configs/sama5d27_wlsom1_ek_qspiflash_defconfig
+++ b/configs/sama5d27_wlsom1_ek_qspiflash_defconfig
@@ -29,6 +29,8 @@
 CONFIG_SPI_BOOT=y
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="sf probe 0; sf read 0x21000000 0x60000 0xc000; sf read 0x22000000 0x6c000 0x394000; bootz 0x22000000 - 0x21000000"
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_DISPLAY_BOARDINFO_LATE=y
 CONFIG_MISC_INIT_R=y