accel/tcg: Declare tcg_flush_jmp_cache() in 'exec/tb-flush.h'

accel/tcg: Declare tcg_flush_jmp_cache() in 'exec/tb-flush.h'

"exec/cpu-common.h" is meant to contain the declarations
related to CPU usable with any accelerator / target
combination.

tcg_flush_jmp_cache() is specific to TCG, so restrict its
declaration by moving it to "exec/tb-flush.h".

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Anton Johansson <anjo@rev.ng>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230918104153.24433-2-philmd@linaro.org>