regulator: cpr3-regulator: add support for max floor to ceiling range

Add support for specifying a maximum floor to ceiling voltage
range for each corner in device tree.  Use the greater of the
original floor voltage and (ceiling voltage - range) as the CPR
floor voltage at runtime.

Change-Id: Ic6b46016d355f315f23ab61813f6df3178bea3ef
Signed-off-by: David Collins <collinsd@codeaurora.org>