PM / OPP: Fix incorrect cpu-supply property in binding

PM / OPP: Fix incorrect cpu-supply property in binding

The regulator bindings allow the "<name>-supply" property to define a
single parent supply and not a list of parents.

Fix the wrong example code present in OPP bindings.

While at it also change the compatible string as Rob pointed out earlier
that none of A7 implementation have multiple supplies for the CPU core.

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