defconfig: msm8916: enable the rpm-smd-regulator driver

Enable the rpm-smd-regulator driver for MSM8916 so that the Linux
kernel running on the application processor can send regulator
requests to the RPM.  The RPM is able to aggregate requests from
all processors to ensure that a minimum sufficient state is used
for regulators at any given time.

Change-Id: Ie4d1250bb63f0525e6eb1f2a94632d3a7b009865
Signed-off-by: David Collins <collinsd@codeaurora.org>