diag: dci: Prevent apps proc from sleeping while processing DCI data

This change prevents apps processor from going to power collapse while
receiving data from the DCI channels. The driver now activates wakeup
sources on arrival of data and releases them upon copying the data
to the user space. This ensures the DCI clients get data while apps
processor is in deep sleep.

Change-Id: Id92d9a5bedc0618efec0d38c850b1ed3977cf08b
Signed-off-by: Ravi Aravamudhan <aravamud@codeaurora.org>