tcg/aarch64: Remove unused code in tcg_out_op

tcg/aarch64: Remove unused code in tcg_out_op

AArch64 defines the TCG_TARGET_HAS_direct_jump. So the "else" block is
useless in the case of "INDEX_op_goto_tb" in function "tcg_out_op". Add
an assertion and delete these codes for clarity.

Suggested-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Qi Hu <huqi@loongson.cn>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20221017020826.990729-1-huqi@loongson.cn>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>