lib: Kconfig: add entry for errno_str() function

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/Kconfig b/lib/Kconfig
index 0454a86..5b6cf3d 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -82,4 +82,12 @@
 	  is performed in hardware.
 endmenu
 
+config ERRNO_STR
+	bool "Enable function for getting errno-related string message"
+	help
+	  The function errno_str(int errno), returns a pointer to the errno
+	  corresponding text message:
+	  - if errno is null or positive number - a pointer to "Success" message
+	  - if errno is negative - a pointer to errno related message
+
 endmenu