This is a preparatory patch required for the next commit which will
start using OPP table's node pointer in _of_init_opp_table(), which
requires the index in order to read the OPP table's phandle.

This commit adds the index argument in the call chains in order to get
it delivered to _of_init_opp_table().
Tested-by: NNiklas Cassel <niklas.cassel@linaro.org>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>