winmm: Clear adwInfo when the struct MMIOINFO is initialized by MMIO_Open

[Bruno Jesus]

On Friday, October 23, 2015, Andrew Eikum <[e-mail]
> wrote:
> This looks OK to me. What do you think about zeroing the whole
> structure instead of just some of the fields, just to prevent this
> problem happening again in the future?

I believe it makes sense, better to have 0 in all fields than garbage.

https://source.winehq.org/patches/data/115723

Thanks,
Bruno