msm: bam_dmux: handle timeouts due to modem crash

If bam_dmux times out waiting for a response from the modem, we assume it
has crashed.  Therefore, prepare for modem restart if enabled, otherwise
report the error with BUG as we are in an unrecoverable state

Change-Id: I5f2419eae721a735a2396693da9fa2d28b14f122
CRs-Fixed: 331808
Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>