Convert CONFIG_UBI_SILENCE_MSG to Kconfig

Signed-off-by: Petr Vorel <petr.vorel@gmail.com>
diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig
index caa5197..cf84783 100644
--- a/drivers/mtd/ubi/Kconfig
+++ b/drivers/mtd/ubi/Kconfig
@@ -1,5 +1,12 @@
 menu "UBI support"
 
+config CONFIG_UBI_SILENCE_MSG
+	bool "UBI silence verbose messages"
+	default ENV_IS_IN_UBI
+	help
+	  Make the verbose messages from UBI stop printing. This leaves
+	  warnings and errors enabled.
+
 config MTD_UBI
 	bool "Enable UBI - Unsorted block images"
 	select CRC32