disp: msm: dp: force disconnect at simulation mode off

Force a disconnect if the simulation client disables simulation
before disconnecting from the simulated sink. This ensures that
the driver will not erroneously attempt AUX transactions in
subsequent interactions after simulation is disabled.

Change-Id: Ibc581deafe46753c514bccc70ba5c953c8d49bd8
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>