qcom: clock: Allow VDD handoff to be optional

Some dedicated power rails do not require a max
voltage vote during bootup, as the rail is completely
under Linux control and is not touched by the bootchain.
Allow clock drivers to skip handoff for the corresponding
VDD classes.

Change-Id: Ia7a7284bea6d10b1785b6710b22ff73b8a0bb23e
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>