target/hexagon/idef-parser: Use gen_constant for gen_extend_tcg_width_op

target/hexagon/idef-parser: Use gen_constant for gen_extend_tcg_width_op

We already have a temporary, res, which we can use for the intermediate
shift result.  Simplify the constant to -1 instead of 0xf*f.
This was the last use of gen_tmp_value, so remove it.

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