msm: board-8930: Add regulator board file for MSM8930+PM8917

Add the board file board-8930-regulator-pm8917.c to capture
regulator configuration and mappings for MSM8930 targets which
utilize a PM8917.  Add code into other MSM8930 board files to
conditionally switch to the new regulator configuration values
if PM8917 is detected at runtime.

Change-Id: I68c1025bae45d77d1a04a8935dc7ecb2d857b8ef
Signed-off-by: David Collins <collinsd@codeaurora.org>