msm: camera: Change API to populate regulator name

Some of the camera modules need to know the
regulator names to enable based on the use case,
Hence change the regulator API to populate regulator
names as well.

Change-Id: I8205df6ecbeed8eca7ff9a81534edadf51309fe1
Signed-off-by: Lakshmi Narayana Kalavala <lkalaval@codeaurora.org>