Add flashmap and u-boot to manifest

Needed to compile the sdk

BUG=b/177367546
TEST=repo init, repo sync
RELEASE_NOTE=None

Change-Id: Icba534904a94b8f3429f207b74e4705d7d5ada0a
Reviewed-on: https://cos-review.googlesource.com/c/cos/manifest/+/34460
Tested-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Reviewed-by: Dexter Rivera <riverade@google.com>

external_full.xml

diff --git a/external_full.xml b/external_full.xml
index 29247b7..fb83e26 100644
--- a/external_full.xml
+++ b/external_full.xml
@@ -63,6 +63,12 @@
   <project path="infra_virtualenv"
            name="mirrors/cros/chromiumos/infra_virtualenv"
            revision="cab8a95f2961561eb56a95d6f2bfc685686db75a" />
+  <project path="src/third_party/u-boot/files"
+           name="mirrors/cros/chromiumos/third_party/u-boot"
+           revision="39ce6d27ad29fd324793a8d0c7db8ae712cc027c" />
+  <project path="src/third_party/flashmap"
+           name="mirrors/cros/chromiumos/third_party/flashmap"
+           revision="2f7b2e16f588dde75a0c9c28175f16b8cb9e11dc" />
 
   <!-- COS sources -->
   <project path="src/overlays"