openrisc: fix typos in comments

Various spelling mistakes in comments.
Detected with the help of Coccinelle.
Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Signed-off-by: Stafford Horne <shorne@gmail.com>

arch/openrisc/mm/tlb.c

@@ -128,7 +128,7 @@ void local_flush_tlb_mm(struct mm_struct *mm)
 
 	/* Was seeing bugs with the mm struct passed to us. Scrapped most of
 	   this function. */
-	/* Several architctures do this */
+	/* Several architectures do this */
 	local_flush_tlb_all();
 }