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/lib/Kconfig b/lib/Kconfig
index d73052d..fe337ac 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -1,5 +1,12 @@
 menu "Library routines"
 
+config BCH
+	bool "Enable Software based BCH ECC"
+	help
+	  Enables software based BCH ECC algorithm present in lib/bch.c
+	  This is used by SoC platforms which do not have built-in ELM
+	  hardware engine required for BCH ECC correction.
+
 config CC_OPTIMIZE_LIBS_FOR_SPEED
 	bool "Optimize libraries for speed"
 	help