doc: Fix typo in doucmentations

Correct typo (double words) in documentations.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt
index 0b23261..e31a2a9 100644
--- a/Documentation/dma-buf-sharing.txt
+++ b/Documentation/dma-buf-sharing.txt
@@ -321,7 +321,7 @@
 
    When the importer is done accessing the range specified in begin_cpu_access,
    it needs to announce this to the exporter (to facilitate cache flushing and
-   unpinning of any pinned resources). The result of of any dma_buf kmap calls
+   unpinning of any pinned resources). The result of any dma_buf kmap calls
    after end_cpu_access is undefined.
 
    Interface: