feat(hftest): double timeouts for coverage runs

If the FVP model is running with the test coverage plugin
configured, double the timeouts to cater for the performance
drop.

Done in both test_spmc.sh for the overall hftest.py timeout,
and inside the hftest.py for each FVP invokation.

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: I4615886029d56c20907f3b3c81721dd866b8dc39
diff --git a/test/hftest/hftest.py b/test/hftest/hftest.py
index 54c51fe..85ed905 100755
--- a/test/hftest/hftest.py
+++ b/test/hftest/hftest.py
@@ -349,7 +349,13 @@
         """Generate command line arguments for FVP."""
         show_output = debug or show_output
         disable_visualisation = self.args.disable_visualisation is True
-        time_limit = "150s" if is_long_running else "40s"
+
+        time_limit = "40s"
+        if self.cov_plugin is None:
+            time_limit = "150s" if is_long_running else time_limit
+        else:
+            time_limit = "300s" if is_long_running else "80s"
+
         fvp_args = []
 
         if not show_output: