scripts/spelling.txt: add "an union" pattern and fix typo instances

Fix typos and add the following to the scripts/spelling.txt:

  an union||a union

Link: http://lkml.kernel.org/r/1481573103-11329-5-git-send-email-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
index e1006b3..bee1404 100644
--- a/include/media/v4l2-ctrls.h
+++ b/include/media/v4l2-ctrls.h
@@ -174,10 +174,10 @@
  *		not freed when the control is deleted. Should this be needed
  *		then a new internal bitfield can be added to tell the framework
  *		to free this pointer.
- * @p_cur:	The control's current value represented via an union with
+ * @p_cur:	The control's current value represented via a union with
  *		provides a standard way of accessing control types
  *		through a pointer.
- * @p_new:	The control's new value represented via an union with provides
+ * @p_new:	The control's new value represented via a union with provides
  *		a standard way of accessing control types
  *		through a pointer.
  */