msm: ipa3: Fix to register client callback in USB/MHI connect

In case of USB/MHI connect/ disconnect the callback registered
is becoming NULL. So, registering the callback at the time
of module initialization.

Change-Id: I2af9206b575728af7f2b8b413022710674ceb485
Signed-off-by: Praveen Kurapati <pkurapat@codeaurora.org>
Signed-off-by: Ashok Vuyyuru <avuyyuru@codeaurora.org>