OPP: Allow same OPP table to be used for multiple genpd

OPP: Allow same OPP table to be used for multiple genpd

The OPP binding says:

	Property: operating-points-v2

	...

	This can contain more than one phandle for power domain
	providers that provide multiple power domains. That is, one
	phandle for each power domain. If only one phandle is available,
	then the same OPP table will be used for all power domains
	provided by the power domain provider.

But the OPP core isn't allowing the same OPP table to be used for
multiple domains. Update dev_pm_opp_of_add_table_indexed() to allow
that.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Rajendra Nayak <rnayak@codeaurora.org>