As the 'Main Loop' section covers softmmu/icount.c,
add "exec/gen-icount.h" there too.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210422064128.2318616-2-f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>