msm: clock-8960: Move DSI resets functionality to their own clocks

The DSI core resets are currently associated with the DSI byte clocks
because the DSI core clocks are managed by the DSI driver directly,
not the clock driver. Move the reset functionality out of the byte
and into their own reset-only branch clocks so that the footswitch
driver, which needs to assert these resets, can do so without
involving the unrelated byte clock.

Change-Id: I2b67ebc6eca343b853f441203874230b8e35f048
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>