target/riscv: Introduce temporary in gen_add_uw()

target/riscv: Introduce temporary in gen_add_uw()

Following the recent changes in translate.c, gen_add_uw() causes
failures on CF3 and SPEC2017 due to the reuse of arg1.  Fix these
regressions by introducing a temporary.

Signed-off-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210911140016.834071-2-philipp.tomsich@vrull.eu
Fixes: 191d1dafae9c ("target/riscv: Add DisasExtend to gen_arith*")
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>