Hexagon (target/hexagon) Move items to DisasContext

Hexagon (target/hexagon) Move items to DisasContext

The following items in the CPUHexagonState are only used for bookkeeping
within the translation of a packet.  With recent changes that eliminate
the need to free TCGv variables, these make more sense to be transient
and kept in DisasContext.

The following items are moved
    dczero_addr
    branch_taken
    this_PC

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230427230012.3800327-22-tsimpson@quicinc.com>