gen_test_desc: support specifying RF-A configuration

Extend the test description to allow specifying RF-A configuration.
All RF-A test configurations are grouped under the rfa-* category.
The expected format for specifying RF-A test configurations is as follows:
rfa_config, rmm_config, tf_config

Change-Id: I335805013057dc7c6c0f520020603a5d8ada67d8
Signed-off-by: Tomás González <tomasagustin.gonzalezorlando@arm.com>
diff --git a/script/build_package.sh b/script/build_package.sh
index a3ba94a..75d3708 100755
--- a/script/build_package.sh
+++ b/script/build_package.sh
@@ -1273,6 +1273,8 @@
 scp_tools_config="$(echo "$build_configs" | awk -F, '{print $4}')"
 spm_config="$(echo "$build_configs" | awk -F, '{print $5}')"
 rmm_config="$(echo "$build_configs" | awk -F, '{print $6}')"
+rfa_config="$(echo "$build_configs" | awk -F, '{print $7}')"
+
 
 test_config_file="$ci_root/group/$test_group/$test_config"