GIC: Add APIs to query interrupt types

These APIs allow the GIC implementation to categorize interrupt numbers
into SPIs, PPIs, and SGIs. The default implementations for GICv2 and
GICv3 follows interrupt numbering as specified by the ARM GIC
architecture.

API documentation updated.

Change-Id: Ia6aa379dc955994333232e6138f259535d4fa087
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
diff --git a/include/plat/common/platform.h b/include/plat/common/platform.h
index 7468352..f00db0d 100644
--- a/include/plat/common/platform.h
+++ b/include/plat/common/platform.h
@@ -73,6 +73,9 @@
  * Optional interrupt management functions, depending on chosen EL3 components.
  ******************************************************************************/
 unsigned int plat_ic_get_running_priority(void);
+int plat_ic_is_spi(unsigned int id);
+int plat_ic_is_ppi(unsigned int id);
+int plat_ic_is_sgi(unsigned int id);
 
 /*******************************************************************************
  * Optional common functions (may be overridden)