Hexagon (target/hexagon) Add overrides for count trailing zeros/ones

Hexagon (target/hexagon) Add overrides for count trailing zeros/ones

The following instructions are overriden
    S2_ct0            Count trailing zeros
    S2_ct1            Count trailing ones
    S2_ct0p           Count trailing zeros (register pair)
    S2_ct1p           Count trailing ones (register pair)

These instructions are not handled by idef-parser because the
imported semantics uses bit-reverse.  However, they are
straightforward to implement in TCG with tcg_gen_ctzi_*

Test cases added to tests/tcg/hexagon/misc.c

Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230405164211.30015-1-tsimpson@quicinc.com>