Turning model based reverse update on for coefs

Turns model based reverse updates on for coefficients in an
effort to reduce the memory requirement for counters.

With this patch the counters needed will be reduced by about
75% since only 3 counts are needed instead of 12.

The impact in performance is:
derf300: -0.252%
stdhd250: -0.046%

However retraining should alleviate some of the drop in
performance.

Change-Id: I6f2b3e13f6d5520aa3400b0b228fb5e8b4a43caa