PM / OPP: Add {opp-microvolt|opp-microamp}-<name> binding

Depending on the version of hardware or its properties, which are only
known at runtime, various properties of the OPP can change. For example,
an OPP with frequency 1.2 GHz, may have different voltage/current
requirements based on the version of the hardware it is running on.

In order to not replicate the same OPP tables for varying values of all
such fields, this commit introduces the concept of opp-property-<name>.
The <name> can be chosen by the platform at runtime, and OPPs will be
initialized depending on that name string. Currently support is extended
for the following properties:
- opp-microvolt-<name>
- opp-microamp-<name>

If the name string isn't provided by the platform, or if it is provided
but doesn't match the properties present in the OPP node, we will fall
back to the original properties without the -<name> string, if they are
available.

Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>