GIC: Add API to get running priority

Document the API in separate platform interrupt controller API document.

Change-Id: If18f208e10a8a243f5c59d226fcf48e985941949
Co-authored-by: Yousuf A <yousuf.sait@arm.com>
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
diff --git a/include/drivers/arm/gicv2.h b/include/drivers/arm/gicv2.h
index a788025..1ef0779 100644
--- a/include/drivers/arm/gicv2.h
+++ b/include/drivers/arm/gicv2.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2017, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -136,6 +136,7 @@
 unsigned int gicv2_acknowledge_interrupt(void);
 void gicv2_end_of_interrupt(unsigned int id);
 unsigned int gicv2_get_interrupt_group(unsigned int id);
+unsigned int gicv2_get_running_priority(void);
 
 #endif /* __ASSEMBLY__ */
 #endif /* __GICV2_H__ */