pstore: Add hsize argument in write_buf call of pstore_ftrace_call

Incorporate the addition of hsize argument in write_buf callback
of pstore. This was forgotten in

    6bbbca73
    pstore: Pass header size in the pstore write callback

Causing a build failure when ftrace and pstore are enabled.
Signed-off-by: Aruna Balakrishnaiah <aruna@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

fs/pstore/ftrace.c

@@ -44,7 +44,7 @@ static void notrace pstore_ftrace_call(unsigned long ip,
 	rec.parent_ip = parent_ip;
 	pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());
 	psinfo->write_buf(PSTORE_TYPE_FTRACE, 0, NULL, 0, (void *)&rec,
-			  sizeof(rec), psinfo);
+			  0, sizeof(rec), psinfo);
 
 	local_irq_restore(flags);
 }