Since 2ac01d6daf, this function does only two things: assert a
lock is held, and call tcg_tb_alloc. It is used exactly once,
and its user has already done the assert.
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Clement Deschamps <clement.deschamps@greensocs.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>