Align default revision with Android version

Certain projects may move forward on their master branch breaking
compatibility with other Android-version-specific projects. This happend
e.g. with the 'kernel/build' project where on the master branch certain
path' and locations have changed.

Thus we have to pin the default revision to the Android and kernel
version we want to build for. This also fixes issue android-rpi#7.

Change-Id: Icf22094caf3521d506acaeb9a3c3f9265d1a877f

default.xml

@@ -1,14 +1,14 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <manifest>
   <remote  name="aosp" fetch="https://android.googlesource.com" review="https://android-review.googlesource.com/" />
-  <default revision="master" remote="aosp" sync-j="4" />
+  <default revision="master-kernel-build-2021" remote="aosp" sync-j="4" />
 
   <superproject name="kernel/superproject" remote="aosp"/>
 
   <project path="build" name="kernel/build" />
   <project path="hikey-modules" name="kernel/hikey-modules" revision="android12-5.10" />
   <project path="common" name="kernel/common" revision="android12-5.10" />
-  <project path="kernel/common-patches" name="kernel/common-patches" >
+  <project path="kernel/common-patches" name="kernel/common-patches" revision="master">
       <linkfile src="android-mainline" dest="common/patches" />
   </project>
   <project path="kernel/tests" name="kernel/tests" />
@@ -19,7 +19,7 @@
   <project path="prebuilts/boot-artifacts" name="platform/prebuilts/boot-artifacts" />
   <project path="prebuilts/build-tools" name="platform/prebuilts/build-tools" clone-depth="1" />
   <project path="prebuilts/kernel-build-tools" name="kernel/prebuilts/build-tools" clone-depth="1" />
-  <project path="tools/mkbootimg" name="platform/system/tools/mkbootimg" />
+  <project path="tools/mkbootimg" name="platform/system/tools/mkbootimg" revision="master" />
 
   <remote  name="arpi" fetch="."/>
   <remove-project name="kernel/common"/>