fvp_mps2.jinja2: Increase --cpulimit to 300 for coverage

Some jobs were spotted which exceeded older limit of 240, e.g.
https://tf.validation.linaro.org/scheduler/job/868138

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I28dfdd911021ee7daf6df5a979b92bda17ff07fc
diff --git a/lava_helper/jinja2_templates/fvp_mps2.jinja2 b/lava_helper/jinja2_templates/fvp_mps2.jinja2
index 21a5d61..426a168 100644
--- a/lava_helper/jinja2_templates/fvp_mps2.jinja2
+++ b/lava_helper/jinja2_templates/fvp_mps2.jinja2
@@ -73,7 +73,7 @@
 {%- if enable_code_coverage %}
     -  "--plugin {CC}"
     -  "--parameter fvp_mps2.UART0.shutdown_tag=\x04"
-    -  "--cpulimit 240"
+    -  "--cpulimit 300"
 {%- endif %}
 
     prompts: