Tidy up spelling

To match the directory "compiler/optimizing" change the spelling of
comments.

Change-Id: I816da4836ce86f4a44ddd2754d8e788d77a27de3
diff --git a/runtime/arch/mips/memcmp16_mips.S b/runtime/arch/mips/memcmp16_mips.S
index aef81af..c8eac9b 100644
--- a/runtime/arch/mips/memcmp16_mips.S
+++ b/runtime/arch/mips/memcmp16_mips.S
@@ -26,7 +26,7 @@
   beqz  $a2,done   /* 0 length string */
   beq $a0,$a1,done    /* strings are identical */
 
-  /* Unoptimised... */
+  /* Unoptimized... */
 1:  lhu $t0,0($a0)
   lhu $t1,0($a1)
   addu  $a1,2