The opp_supported_hw DT property allows the DT to specify a mask of chip
revisions that a certain OPP is eligible for. This allows for easy
limiting of maximum frequencies, for instance.

Add support for that in the sun50i-cpufreq-nvmem driver. We support both
the existing opp-microvolt suffix properties as well as the
opp-supported-hw property, the generic code figures out which is needed
automatically.
However if none of the DT OPP nodes contain an opp-supported-hw
property, the core code will ignore all OPPs and the driver will fail
probing. So check the DT's eligibility first before using that feature.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>