sgi/boot: allow boot test script to be usable on SGI-Clark.Ares platform

Add SGI-Clark.Ares platform as a supported platform in busybox boot test
script.

Change-Id: I890ca1f9f02fb07c52e3fd0b398a2224eeca404f
Signed-off-by: Chandni Cherukuri <chandni.cherukuri@arm.com>

sgi/boot.sh

@@ -35,6 +35,7 @@ source sgi_common_util.sh
 
 declare -A sgi_platforms
 sgi_platforms[sgi575]=1
+sgi_platforms[sgiclarka]=1
 
 __print_supported_sgi_platforms()
 {