ubispl: introduce separate CONFIG_UBI_SPL_SILENCE_MSG

This allows to silence ubi and ubispl individually.

Signed-off-by: Markus Klotzbuecher <markus.klotzbuecher@kistler.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
Cc: Kyungmin Park <kmpark@infradead.org>
diff --git a/common/spl/Kconfig b/common/spl/Kconfig
index 716b1ec..8021661 100644
--- a/common/spl/Kconfig
+++ b/common/spl/Kconfig
@@ -702,6 +702,12 @@
 	help
 	  The UBI volume id from which to load the device tree
 
+config UBI_SPL_SILENCE_MSG
+	bool "silence UBI SPL messages"
+	default n
+	help
+	  Disable messages from UBI SPL. This leaves warnings
+	  and errors enabled.
 
 endif   # if SPL_UBI