Unmask SError and Debug exceptions.

Any asynchronous exception caused by the firmware should be handled
in the firmware itself.  For this reason, unmask SError exceptions
(and Debug ones as well) on all boot paths.  Also route external
abort and SError interrupts to EL3, otherwise they will target EL1.

Change-Id: I9c191d2d0dcfef85f265641c8460dfbb4d112092
diff --git a/common/psci/psci_private.h b/common/psci/psci_private.h
index 48d40d0..6505adf 100644
--- a/common/psci/psci_private.h
+++ b/common/psci/psci_private.h
@@ -64,6 +64,7 @@
 	unsigned long tcr;
 	unsigned long ttbr;
 	unsigned long vbar;
+	unsigned long pstate;
 } secure_context;
 
 /*******************************************************************************