regulator: cpr3-regulator: add support for dynamic floor voltage

Add support for a CPR dynamic floor voltage.  This voltage
corresponds to the last known closed-loop voltage of the
specified corner for a given CPR3 regulator.  It is imposed
as a global CPR floor whenever all of the power domains for
the CPR3 regulator are bypassed.

This feature can be used to ensure that the vdd-supply voltage
is never driven below the functional voltage of a power
collapsed processor due to down step recommendations from a
processor that is not power collapsed.

Change-Id: I9066b499c3b303928f1d81fbd1b1c5f991cee233
Signed-off-by: David Collins <collinsd@codeaurora.org>