PM / OPP: Add missing of_node_put(np)

PM / OPP: Add missing of_node_put(np)

The for_each_available_child_of_node() loop in _of_add_opp_table_v2()
doesn't drop the reference to "np" on errors. Fix that.

Fixes: 274659029c9d (PM / OPP: Add support to parse "operating-points-v2" bindings)
Cc: 4.3+ <stable@vger.kernel.org> # 4.3+
Signed-off-by: Tobias Jordan <Tobias.Jordan@elektrobit.com>
[ VK: Improved commit log. ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>