ubifs: Define UBIFS crypto context xattr

Like ext4 UBIFS will store the crypto context in a xattr
attribute.
Signed-off-by: Richard Weinberger <richard@nod.at>

fs/ubifs/ubifs-media.h

@@ -300,6 +300,13 @@ enum {
 /* The largest UBIFS node */
 #define UBIFS_MAX_NODE_SZ UBIFS_MAX_INO_NODE_SZ
 
+/*
+ * xattr name of UBIFS encryption context, we don't use a prefix
+ * nor a long name to not waste space on the flash.
+ */
+#define UBIFS_XATTR_NAME_ENCRYPTION_CONTEXT "c"
+
+
 /*
  * On-flash inode flags.
  *