target-arm: Use tcg_gen_extrh_i64_i32

target-arm: Use tcg_gen_extrh_i64_i32

Usually, eliminate an operation from the translator by combining
a shift with an extract.

In the case of gen_set_NZ64, we don't need a boolean value for cpu_ZF,
merely a non-zero value.  Given that we can extract both halves of a
64-bit input in one call, this simplifies the code.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Message-id: 1441909103-24666-12-git-send-email-rth@twiddle.net
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>