trivial: fix then -> than typos in comments and documentation

- (better, more, bigger ...) then -> (...) than

Signed-off-by: Frederik Schwarzer <schwarzerf@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/mtd/ubi/io.c b/drivers/mtd/ubi/io.c
index a74118c..fe81039 100644
--- a/drivers/mtd/ubi/io.c
+++ b/drivers/mtd/ubi/io.c
@@ -465,7 +465,7 @@
  * This function synchronously erases physical eraseblock @pnum. If @torture
  * flag is not zero, the physical eraseblock is checked by means of writing
  * different patterns to it and reading them back. If the torturing is enabled,
- * the physical eraseblock is erased more then once.
+ * the physical eraseblock is erased more than once.
  *
  * This function returns the number of erasures made in case of success, %-EIO
  * if the erasure failed or the torturing test failed, and other negative error