misc,python: Add pre-commit-hook-yamlfmt to pre-commit

This automatically formats .yaml files. By deault has the following
parameters:

* `mapping`: 4 spaces.
* `sequence`: 6 spaces.
* `offset`: 4 spaces.
* `colons`: do not align top-level colons.
* `width`: None.

Change-Id: Iee5194cd57b7b162fd7e33aa6852b64c5578a3d2

.pre-commit-config.yaml

@@ -1,3 +1,4 @@
+---
 # Copyright (c) 2022 Arm Limited
 # All rights reserved.
 #
@@ -33,7 +34,7 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-minimum_pre_commit_version: "2.18"
+minimum_pre_commit_version: '2.18'
 
 default_language_version:
     python: python3
@@ -62,6 +63,10 @@ repos:
           - id: mixed-line-ending
             args: [--fix=lf]
           - id: check-case-conflict
+    - repo: https://github.com/jumanjihouse/pre-commit-hook-yamlfmt
+      rev: 0.2.3
+      hooks:
+          - id: yamlfmt
     - repo: https://github.com/psf/black
       rev: 22.6.0
       hooks:
@@ -72,18 +77,18 @@ repos:
             name: gem5 style checker
             entry: util/git-pre-commit.py
             always_run: true
-    exclude: ".*"
+            exclude: .*
             language: system
-    description: 'The gem5 style checker hook.'
+            description: The gem5 style checker hook.
           - id: gem5-commit-msg-checker
             name: gem5 commit msg checker
             entry: ext/git-commit-msg
             language: system
             stages: [commit-msg]
-    description: 'The gem5 commit message checker hook.'
+            description: The gem5 commit message checker hook.
           - id: gerrit-commit-msg-job
             name: gerrit commit message job
             entry: util/gerrit-commit-msg-hook
             language: system
             stages: [commit-msg]
-    description: 'Adds Change-ID to the commit message. Needed by Gerrit.'
+            description: Adds Change-ID to the commit message. Needed by Gerrit.