Convert CONFIG_CMD_BSP to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_BSP

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/charon_defconfig b/configs/charon_defconfig
index 3dd1588..4e29234 100644
--- a/configs/charon_defconfig
+++ b/configs/charon_defconfig
@@ -17,6 +17,7 @@
 CONFIG_CMD_PING=y
 CONFIG_CMD_SNTP=y
 CONFIG_CMD_BMP=y
+CONFIG_CMD_BSP=y
 CONFIG_CMD_EXT2=y
 CONFIG_CMD_FAT=y
 CONFIG_MAC_PARTITION=y