doc: Fix typo "is is" in Documentations

Fix double words "is is" in Documentations.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Rob Landley <rob@landley.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/Documentation/mtd/nand_ecc.txt b/Documentation/mtd/nand_ecc.txt
index 990efd7..e129b24 100644
--- a/Documentation/mtd/nand_ecc.txt
+++ b/Documentation/mtd/nand_ecc.txt
@@ -543,7 +543,7 @@
     }
 
 As you can see tmppar is used to accumulate the parity within a for
-iteration. In the last 3 statements is is added to par and, if needed,
+iteration. In the last 3 statements is added to par and, if needed,
 to rp12 and rp14.
 
 While making the changes I also found that I could exploit that tmppar