msm: acpuclock-krait: Migrate to rpm_regulator_*() APIs

Support for rpm_vreg_set_voltage is not supported on newer targets like
msm-copper. It has been replaced by the rpm_regulator_*() family of
APIs. Update acpuclock-krait accordingly.

Change-Id: I980aeff025f15239b2ecf11133afd770ee13bba1
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>