tfa-next(next-checks-clippy): use rust Makefile to list platforms

tfa-next has added a new `list_platforms` target for the
rust/Makefile. Use this target instead of hardcoding the available
platforms.

Change-Id: I5701e366b5cf4f3ba8a8f5d58a02ed08237cc353
Signed-off-by: Tomás González <tomasagustin.gonzalezorlando@arm.com>
diff --git a/script/next-checks/next-checks-clippy.sh b/script/next-checks/next-checks-clippy.sh
index b7a644a..4b07b33 100755
--- a/script/next-checks/next-checks-clippy.sh
+++ b/script/next-checks/next-checks-clippy.sh
@@ -19,7 +19,9 @@
 echo >> "$LOG_TEST_FILENAME"
 echo "Platforms:" >> "$LOG_TEST_FILENAME"
 
-for plat in "fvp" "qemu"
+available_platforms=$(make -C ${TF_ROOT}/rust list_platforms)
+
+for plat in $available_platforms
 do
     echo >> $LOG_FILE
     echo "############### ${TEST_CASE} - platform: ${plat}" >> "$LOG_FILE"