OPP: Don't take OPP table's kref for static OPPs

The reference count is only required to be incremented for every call
that may lead to adding the OPP table. For static OPPs the same should
be done from the parent routine which adds all static OPPs together and
so only one refcount for all static OPPs.

Update code to reflect that.

The refcount is incremented every time a dynamic OPP is created (as that
can lead to creating the OPP table) and the same is dropped when the OPP
is removed.

Tested-by: Niklas Cassel <niklas.cassel@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>