clk: msm: clock-local2: Add get_parent for display clocks

On some hardware, the display byte and pixel clocks can have multiple
parents and we can switch between them dynamically. To support this
add a new set of ops. Also implement the get_parent for these clocks
so that handoff code can dynamically set the parent for these clocks
instead of relying on the parent field to be set up explicitly when
definining the structures for those clocks. On hardware which does not
support dynamically switching parents, the old set of ops can still be
used.

Change-Id: Ia076652124df40fa5a62d0f7041b5afed121aae9
Signed-off-by: Pushkar Joshi <pushkarj@codeaurora.org>