pmic-voter: disassociate device from votables

Currently the pmic votables need a device to be created.
Votables should be able to work on device less code. Remove
the need for device and instead use a void pointer to be passed
back to the callback.

CRs-Fixed: 1018090
Change-Id: If5dafbcc0d88596332b794ad5b6fdc1f9ff98a45
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>