ARM: dts: msm: specify dynamic VDD_APCC CPR floor voltages for msm8996v2

Specify a maximum floor to ceiling voltage range for each
VDD_APCC corner.  Also reduce the fixed floor voltages to 470 mV
which is the absolute minimum functional voltage.  This ensures
that closed-loop CPR is able to drive the VDD_APCC voltage lower
than the previously defined fixed floor voltages.

Change-Id: I55722dde6080559da2a622b88f3bc7225c9888bd
Signed-off-by: David Collins <collinsd@codeaurora.org>