target/arm: Make the t32 insn[25:23]=111 group non-overlapping

The t32 decode has a group which represents a set of insns
which overlap with B_cond_thumb because they have [25:23]=111
(which is an invalid condition code field for the branch insn).
This group is currently defined using the {} overlap-OK syntax,
but it is almost entirely non-overlapping patterns. Switch
it over to use a non-overlapping group.

For this to be valid syntactically, CPS must move into the same
overlapping-group as the hint insns (CPS vs hints was the
only actual use of the overlap facility for the group).

The non-overlapping subgroup for CLREX/DSB/DMB/ISB/SB is no longer
necessary and so we can remove it (promoting those insns to
be members of the parent group).

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20201019151301.2046-5-peter.maydell@linaro.org