powerpc/eeh: Export confirm_error_lock

This exports @confirm_error_lock so that eeh_serialize_{lock, unlock}()
can be used to freeze the affected PE in PCI surprise hot remove path.
Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/eeh.c

@@ -116,6 +116,7 @@ struct eeh_ops *eeh_ops = NULL;
 
 /* Lock to avoid races due to multiple reports of an error */
 DEFINE_RAW_SPINLOCK(confirm_error_lock);
+EXPORT_SYMBOL_GPL(confirm_error_lock);
 
 /* Lock to protect passed flags */
 static DEFINE_MUTEX(eeh_dev_mutex);