OPP: Pass OPP table to _of_add_opp_table_v{1|2}()

Both _of_add_opp_table_v1() and _of_add_opp_table_v2() contain similar
code to get the OPP table and their parent routine also parses the DT to
find the OPP table's node pointer. This can be simplified by getting the
OPP table in advance and then passing it as argument to these routines.

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