spcom: print error messages when remote SP subsystem crash

When the remote Secure Processor (SP) subsystem crash (SSR), the
communication link goes down. Print error messages for this rare event.

Change-Id: Ib3f719e218d972b75936d9960e342ecfe6787301
Signed-off-by: Amir Samuelov <amirs@codeaurora.org>