Unnest independent dexpreopt conditionals

Most of the 6 nested conditionals are independent and can be
evaluated individually.  This has a slight change in behavior,
disabling preopt for a module in the product will now override
LOCAL_DEX_PREOPT, but that seems preferable.

Test: m
Change-Id: I6a4060a78df729c34bbf6978c84993859a947bf7