Add u-boot repo, pvmfw branch by default

Change-Id: Ifc192da38e3aa9e296f664482b25454d4d4fd675
diff --git a/default.xml b/default.xml
index 888d834..1f029c6 100644
--- a/default.xml
+++ b/default.xml
@@ -12,6 +12,8 @@
   <project path="kvm-unit-tests" name="kvm-unit-tests" revision="kvmunittests" />
   <project path="linux" name="linux" revision="pkvm" />
   <project path="misc" name="misc" />
+  <project path="u-boot" name="u-boot" revision="pvmfw" />
+
   <project path="prebuilts" name="prebuilts" clone-depth="1" />
   <project path="toolchains/linux-x86/gcc" name="toolchains/linux-x86/gcc" clone-depth="1" />