Upgrade AOSP tag to r20

This patch will update the AOSP tag to r20

Tests Done: Build and boot

Tracked-On: OAM-131768
Change-Id: Idc3f3b8e06a2771782ec955e8363b156e93e94af
Signed-off-by: Tekriwal, Tanuj <tanuj.tekriwal@intel.com>
Signed-off-by: iviggyprabhu <vignesh.t.prabhu@intel.com>

Author: iViggyPrabhu

default.xml

@@ -3,7 +3,7 @@
 
    <remote  name="aosp"
             fetch="https://android-review.googlesource.com" />
-   <default revision="refs/tags/android-15.0.0_r9"
+   <default revision="refs/tags/android-15.0.0_r20"
             remote="aosp"
             sync-j="7" />