tcg: Replace asserts on tcg_jmp_insn_offset

Test TCG_TARGET_HAS_direct_jump instead of testing an
implementation pointer.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
6 files changed