GIC: Add API to raise secure SGI

API documentation updated.

Change-Id: I129725059299af6cc612bafa8d74817f779d7c4f
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
diff --git a/include/plat/common/platform.h b/include/plat/common/platform.h
index c97b7d3..b4e33d9 100644
--- a/include/plat/common/platform.h
+++ b/include/plat/common/platform.h
@@ -82,6 +82,7 @@
 int plat_ic_has_interrupt_type(unsigned int type);
 void plat_ic_set_interrupt_type(unsigned int id, unsigned int type);
 void plat_ic_set_interrupt_priority(unsigned int id, unsigned int priority);
+void plat_ic_raise_el3_sgi(int sgi_num, u_register_t target);
 
 /*******************************************************************************
  * Optional common functions (may be overridden)