feat(sbsa): helper api for refreshing watchdog timer

This patch adds a helper API to explicitly refresh SBSA secure watchdog
timer. Please refer section A.3 of the following spec:

https://developer.arm.com/documentation/den0029/latest/

Change-Id: I2d0943792aea0092bee1e51d74b908348587e66b
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
diff --git a/changelog.yaml b/changelog.yaml
index 6dbb9b2..c969b2c 100644
--- a/changelog.yaml
+++ b/changelog.yaml
@@ -877,6 +877,9 @@
                 deprecated:
                   - drivers/tzc380
 
+          - title: SBSA
+            scope: sbsa
+
       - title: Marvell
         scope: marvell-drivers