defconfig: arm64: msm: enable rpmh-regulator driver for msmskunk

Enable the rpmh-regulator driver so that consumers can utilize
PMIC regulators which are managed by the RPMh hardware blocks
on MSMSKUNK.

Change-Id: Iec62cf2d2755483ce0e281e87ca7cddc1d98e0a9
CRs-Fixed: 1082230
Signed-off-by: David Collins <collinsd@codeaurora.org>