clk: msm: clock-cpu-8996: round clock rates to nearest fmax frequency

Modify the round_rate() callback function so that it selects
the nearest configured fmax frequency instead of the closest
possible supported frequency of the parent clock.  This ensures
that clk_round_rate() always returns power efficient frequencies
for 8996 CPU clocks.

Change-Id: Icc27ba64b9c8af74ee0f81443fea37c4564b9f94
CRs-Fixed: 981475
Signed-off-by: David Collins <collinsd@codeaurora.org>