powerpc/powernv: Change BUG_ON to WARN_ON in elog code

We can continue to read the error log (up to MAX size) even if
we get the elog size more than MAX size. Hence change BUG_ON to
WARN_ON.

Also updated error message.
Reported-by: NGopesh Kumar Chaudhary <gopchaud@in.ibm.com>
Signed-off-by: NVasant Hegde <hegdevasant@linux.vnet.ibm.com>
Signed-off-by: NAnanth N Mavinakayanahalli <ananth@in.ibm.com>
Acked-by: NDeepthi Dharwar <deepthi@linux.vnet.ibm.com>
Acked-by: NStewart Smith <stewart@linux.vnet.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/powernv/opal-elog.c

@@ -249,7 +249,7 @@ static void elog_work_fn(struct work_struct *work)
 
 	rc = opal_get_elog_size(&id, &size, &type);
 	if (rc != OPAL_SUCCESS) {
-		pr_err("ELOG: Opal log read failed\n");
+		pr_err("ELOG: OPAL log info read failed\n");
 		return;
 	}
 
@@ -257,7 +257,7 @@ static void elog_work_fn(struct work_struct *work)
 	log_id = be64_to_cpu(id);
 	elog_type = be64_to_cpu(type);
 
-	BUG_ON(elog_size > OPAL_MAX_ERRLOG_SIZE);
+	WARN_ON(elog_size > OPAL_MAX_ERRLOG_SIZE);
 
 	if (elog_size >= OPAL_MAX_ERRLOG_SIZE)
 		elog_size  =  OPAL_MAX_ERRLOG_SIZE;