clk: clock-pll: Support parsing votable plls from dt

Add functionality to load votable and active-sleep PLLs
from device tree. Active/sleep PLLs, like RPM clocks,
support "active" and "sleep" modes of operation.

Change-Id: I997dfb5b51afeade7e1dde0e183b47f870f22bdd
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>