winmm/tests: Allow more margin in the test_asyncWAVE() playback check.

[Joerg-Cyril.Hoehle at t-systems.com]

>> I suggest adding a todo_wine plus an additional
>> ok(0<p2 && strcmp(buf,"2000")) that Wine won't fail.
>Ok. I think this can still be narrower, 400-1000ms for instance

I meant to have 2 tests
ok(0<p2 && strcmp(buf,"2000")) -- not narrowed, just to prevent complete breakage
todo_wine ok(100<=p2 && p2<=300) -- as narrow as you see fit