target/arm: Convert division from feature bits to isar0 tests

target/arm: Convert division from feature bits to isar0 tests

Both arm and thumb2 division are controlled by the same ISAR field,
which takes care of the arm implies thumb case.  Having M imply
thumb2 division was wrong for cortex-m0, which is v6m and does not
have thumb2 at all, much less thumb2 division.

Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Signed-off-by: Richard Henderson <[email protected]>
Message-id: 20181016223115[email protected]
Reviewed-by: Peter Maydell <[email protected]>
Signed-off-by: Peter Maydell <[email protected]>