feat(ast2700): add Aspeed AST2700 platform support

Aspeed AST2700 is a quad-core SoC with ARM Cortex-A35 integrated.
This patch adds the initial platform support for AST2700 and also
updates the documents.

Change-Id: I1796f7aae5ed2d1799e91fabb8949607959cd9b3
Signed-off-by: Chia-Wei Wang <chiawei_wang@aspeedtech.com>
diff --git a/changelog.yaml b/changelog.yaml
index 0c4644d..0a97743 100644
--- a/changelog.yaml
+++ b/changelog.yaml
@@ -244,6 +244,13 @@
           - title: Corstone-1000
             scope: corstone-1000
 
+      - title: Aspeed
+        scope: aspeed
+
+        subsections:
+          - title: AST2700
+            scope: ast2700
+
       - title: Broadcom
         scope: brcm