Documentation/: it's -> its where appropriate

Fix obvious cases of "it's" being used when "its" was meant.

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/Documentation/filesystems/nfs/rpc-cache.txt b/Documentation/filesystems/nfs/rpc-cache.txt
index 8a382be..ebcaaee 100644
--- a/Documentation/filesystems/nfs/rpc-cache.txt
+++ b/Documentation/filesystems/nfs/rpc-cache.txt
@@ -185,7 +185,7 @@
 request/response format
 -----------------------
 
-While each cache is free to use it's own format for requests
+While each cache is free to use its own format for requests
 and responses over channel, the following is recommended as
 appropriate and support routines are available to help:
 Each request or response record should be printable ASCII