msm: cpr-regulator: change device tree vendor prefix to 'qti'

New policy requires changing device tree vendor prefix from 'qcom'
to 'qti'. Also change device tree files for msm8610, msm8226 and msm8926.

Change-Id: I57c8c9d14ffa3ddd3671f406cfa2011eb23e66e4
Signed-off-by: Ke Liu <keliu@codeaurora.org>