ARM: dts: msm: reduce CPU LDO headroom voltage for msm8996pro

Hardware characterization has shown that the CPU LDOs can
operate safely with less than 150 mV of headroom voltage.
Reduce the CPU LDO minimum allowed headroom voltage for both the
power cluster and the performance cluster in order to save power
by allowing LDO usage in more situations.

Change-Id: I72f28569d4719540fc84cf65d8783bbfec9435ad
CRs-Fixed: 989555
Signed-off-by: David Collins <collinsd@codeaurora.org>