target-microblaze: Use tcg_gen_movcond in eval_cond_jmp

Cleanup eval_cond_jmp to use tcg_gen_movcond_i64().
No functional change.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>