wasapisink: Re-align device period if necessary

wasapisink: Re-align device period if necessary

Sometimes the minimum period advertised by a card results in an
unaligned buffer size error during initialization in exclusive mode.
In that case, we can fetch the actual buffer size in frames and
calculate the period from that.

We can't do this pre-emptively because we can't call GetBufferSize
till Initialize has been called at least once.

https://bugzilla.gnome.org/show_bug.cgi?id=793289