n1sdp: Enable the NEOVERSE_N1_EXTERNAL_LLC flag

Since N1SDP has a system level cache which is an
external LLC enable the NEOVERSE_N1_EXTERNAL_LLC flag.

Change-Id: Idb34274e61e7fd9db5485862a0caa497f3e290c7
Signed-off-by: Chandni Cherukuri <chandni.cherukuri@arm.com>

plat/arm/board/n1sdp/platform.mk

@@ -63,6 +63,9 @@ HW_ASSISTED_COHERENCY			:=	1
 # When building for systems with hardware-assisted coherency, there's no need to
 # use USE_COHERENT_MEM. Require that USE_COHERENT_MEM must be set to 0 too.
 USE_COHERENT_MEM			:=	0
+
+# Enable the flag since N1SDP has a system level cache
+NEOVERSE_N1_EXTERNAL_LLC		:=	1
 include plat/arm/common/arm_common.mk
 include plat/arm/css/common/css_common.mk
 include plat/arm/board/common/board_common.mk