Hexagon (target/hexagon) Short-circuit more HVX single instruction packets

Hexagon (target/hexagon) Short-circuit more HVX single instruction packets

The generated helpers for HVX use pass-by-reference, so they can't
short-circuit when the reads/writes overlap.  The instructions with
overrides are OK because they use tcg_gen_gvec_*.

We add a flag has_hvx_helper to DisasContext and extend gen_analyze_funcs
to set the flag when the instruction is an HVX instruction with a
generated helper.

We add an override for V6_vcombine so that it can be short-circuited
along with a test case in tests/tcg/hexagon/hvx_misc.c

Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230427230012.3800327-15-tsimpson@quicinc.com>