accel/tcg: Compile watchpoint.c once

accel/tcg: Compile watchpoint.c once

Move tb_check_watchpoint declaration from tb-internal.h, which is
still target-specific, to internal-common.h, which isn't.
Otherwise, all that is required to build watchpoint.c once is
to include the new exec/cpu-interrupt.h instead of exec/exec-all.h.

Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>