target/arm: Convert VFM[AS]L (vector) to decodetree

target/arm: Convert VFM[AS]L (vector) to decodetree

Convert the VFM[AS]L (vector) insns to decodetree.  This is the last
insn in the legacy decoder for the 3same_ext group, so we can
delete the legacy decoder function for the group entirely.

Note that in disas_thumb2_insn() the parts of this encoding space
where the decodetree decoder returns false will correctly be directed
to illegal_op by the "(insn & (1 << 28))" check so they won't fall
into disas_coproc_insn() by mistake.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200430181003.21682-8-peter.maydell@linaro.org