diag: Replace wait_event with wait_event_interruptible

Diag driver puts the process that waits for data from peripherals
to an uninterruptible sleep. Make changes in the diag driver to
use the alternative wait that can be interruptible by signals.

Change-Id: I428475b7a14aa4d559fcf08ccc459c49d21974f5
Signed-off-by: Ravi Aravamudhan <aravamud@codeaurora.org>