plat/fvp: Add support for dynamic description of secure interrupts

Using the fconf framework, the Group 0 and Group 1 secure interrupt
descriptors are moved to device tree and retrieved in runtime. This
feature is enabled by the build flag SEC_INT_DESC_IN_FCONF.

Change-Id: I360c63a83286c7ecc2426cd1ff1b4746d61e633c
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
diff --git a/make_helpers/defaults.mk b/make_helpers/defaults.mk
index e5880d2..585f06f 100644
--- a/make_helpers/defaults.mk
+++ b/make_helpers/defaults.mk
@@ -226,7 +226,10 @@
 ARM_IO_IN_DTB			:= 0
 
 # Build option to support SDEI through fconf
-SDEI_IN_FCONF			:=0
+SDEI_IN_FCONF			:= 0
+
+# Build option to support Secure Interrupt descriptors through fconf
+SEC_INT_DESC_IN_FCONF		:= 0
 
 # Build option to choose whether Trusted Firmware uses library at ROM
 USE_ROMLIB			:= 0