diag: Fix problem with stopping of logging data

On-Device Logging at very high logging rates can cause
a race condition where the buffers reading in data from
the smd channel are filled with data and are not having
their data logged to userspace.  Detect this condition
and restart the logging process.

CRs-Fixed: 382128
Change-Id: I3bb4cfae1bd72d2575c32e800973fac558beae7c
Signed-off-by: Dixon Peterson <dixonp@codeaurora.org>