website: Update documentation.yml to include new ARM files.

The new files on power modelling and adding DVFS support to ARM FS
simultations were not in the tabs on the website. This has now been
fixed.

Change-Id: Ifba9cc55d7673949bef425d6cf8c526bfeb55862
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-website/+/36680
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Ciro Santilli <ciro.santilli@arm.com>
diff --git a/_data/documentation.yml b/_data/documentation.yml
index b999970..407b99c 100755
--- a/_data/documentation.yml
+++ b/_data/documentation.yml
@@ -211,6 +211,10 @@
           url: /documentation/learning_gem5/part1/example_configs
         - page: Extending gem5 for ARM
           url: /documentation/learning_gem5/part1/extending_configs
+        - page: ARM Power Modelling
+          url: /documentation/learning_gem5/part1/arm_power_modelling
+        - page: ARM DVFS Support
+          url: /documentation/learning_gem5/part1/arm_dvfs_support
 
     - title: Modifying/Extending
       id: part2