msm: clock-8610: fix the unbalanced DSI AHB clock issue

The DSI AHB clock is unblanced during the hand-off operation.
During early_init, clock driver hands off clocks, prepare_count
is raised to 1 for all dsi clocks.

Later on, display driver prepares the dsi clocks, they reference
count raised to 2, but DSI AHB clock reference count is still 1,
as the dsi clocks are already enabled.

At late_init time, clock driver reduces the refcount of the dsi
clocks by 1.  The DSI AHB clock ref count is now zero, while
the other DSI clock ref count is 1.

This creates the unbalanced DSI AHB clock.

Change-Id: I35734d05120a12261d228dcffec1e84ea1a32255
Signed-off-by: Xiaoming Zhou <zhoux@codeaurora.org>