max_m5: wait FSTAT.DNR ready before loading model

Conusult with Maxim, we need to wait DNT bit 0 before loading model.
The DNR bit indicates “Data Not Ready”, and is not cleared until
the firmware performs its entire list of calculations.

Bug: 200039507
Signed-off-by: Jenny Ho <hsiufangho@google.com>
Change-Id: I1672612229eb9572245fd413ebadeb42ebd844b2