feat(hcx): add TF, TFTF, and group entries for FEAT_HCX

This patch adds support for automated test of TF-A support for
enabling FEAT_HCX. This feature can't be tested through normal means
since some models support it and others don't, and the TFTF test has
no way of knowing whether or not its been enabled in the TF-A build
in use.

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I374e191db3b61c43362b54c8d2c2c38e806e8aaf
diff --git a/tf_config/fvp-default-hcx b/tf_config/fvp-default-hcx
new file mode 100644
index 0000000..c5660aa
--- /dev/null
+++ b/tf_config/fvp-default-hcx
@@ -0,0 +1,3 @@
+CROSS_COMPILE=aarch64-none-elf-
+PLAT=fvp
+ENABLE_FEAT_HCX=1