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/am3517_evm_defconfig b/configs/am3517_evm_defconfig
index d03850b..27ea7a4 100644
--- a/configs/am3517_evm_defconfig
+++ b/configs/am3517_evm_defconfig
@@ -41,4 +41,5 @@
 CONFIG_USB=y
 CONFIG_USB_MUSB_HOST=y
 CONFIG_USB_STORAGE=y
+CONFIG_BCH=y
 CONFIG_OF_LIBFDT=y