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/a3m071_defconfig b/configs/a3m071_defconfig
index d485a0c..8d636e0 100644
--- a/configs/a3m071_defconfig
+++ b/configs/a3m071_defconfig
@@ -21,6 +21,7 @@
 CONFIG_CMD_MII=y
 CONFIG_CMD_PING=y
 CONFIG_CMD_LINK_LOCAL=y
+CONFIG_CMD_BSP=y
 CONFIG_CMD_CACHE=y
 CONFIG_CMD_UBI=y
 # CONFIG_MMC is not set