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>

fs/proc/task_nommu.c

@@ -9,7 +9,7 @@
 
 /*
  * Logic: we've got two memory sums for each process, "shared", and
- * "non-shared". Shared memory may get counted more then once, for
+ * "non-shared". Shared memory may get counted more than once, for
  * each process that owns it. Non-shared memory is counted
  * accurately.
  */