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/DocBook/libata.tmpl b/Documentation/DocBook/libata.tmpl
index ba99757..261b57b 100644
--- a/Documentation/DocBook/libata.tmpl
+++ b/Documentation/DocBook/libata.tmpl
@@ -490,7 +490,7 @@
 	allocates space for a legacy IDE PRD table and returns.
 	</para>
 	<para>
-	->port_stop() is called after ->host_stop().  It's sole function
+	->port_stop() is called after ->host_stop().  Its sole function
 	is to release DMA/memory resources, now that they are no longer
 	actively being used.  Many drivers also free driver-private
 	data from port at this time.