intel: Give an explanation why we are exiting for debugging.

This could happen in 3 different cases, and ERRNO can explain what
happened. First case would be EIO (gpu hang), second EINVAL (something is
wrong inside the batch), and we also discovered that sometimes it happens
with ENOSPACE. All of those cases are different it it could be worth to at
least know what happened.

Signed-off-by: Eugeni Dodonov <eugeni.dodonov@intel.com>

src/mesa/drivers/dri/intel/intel_batchbuffer.c

@@ -138,6 +138,7 @@ do_flush_locked(struct intel_context *intel)
    }
 
    if (ret != 0) {
+      fprintf(stderr, "intel_do_flush_locked failed: %s\n", strerr(ret));
       exit(1);
    }
    intel->vtbl.new_batch(intel);