twsi: use tsleep instead of pause for better responsiveness

wakeup() does not have any effect on pause(), so if a transfer was
not finished by the time of the first check, then the thread
would sleep full 30 ms.

To do: protect the transfer and interrupt code with the mutex,
switch from tsleep from msleep

Reviewed by: manu
MFC after: 3 weeks
Differential Revision: https://reviews.freebsd.org/D26309