Convert CONFIG_BCH to Kconfig

This converts the following to Kconfig:
   CONFIG_BCH

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/x600_defconfig b/configs/x600_defconfig
index 91cf93f..bcb20fa 100644
--- a/configs/x600_defconfig
+++ b/configs/x600_defconfig
@@ -44,6 +44,7 @@
 CONFIG_USB=y
 CONFIG_USB_EHCI_HCD=y
 CONFIG_USB_STORAGE=y
+CONFIG_BCH=y
 CONFIG_USE_TINY_PRINTF=y
 CONFIG_OF_LIBFDT=y
 # CONFIG_EFI_LOADER is not set