brillo manifest: Add Brillo 4.1 common kernel

Add the Brillo common kernel
diff --git a/default.xml b/default.xml
index e019aeb..5e3560f 100644
--- a/default.xml
+++ b/default.xml
@@ -129,6 +129,7 @@
   <project path="frameworks/native" name="platform/frameworks/native" groups="pdk,bdk" />
   <project path="frameworks/rs" name="platform/frameworks/rs" groups="pdk,bdk" />
   <project path="hardware/bsp/kernel/common/android-3.18" name="kernel/common" revision="android-3.18" groups="bdk" />
+  <project path="hardware/bsp/kernel/common/v4.1" name="platform/hardware/bsp/kernel/common/v4.1" groups="bdk" />
   <project path="hardware/libhardware" name="platform/hardware/libhardware" groups="pdk,bdk" />
   <project path="hardware/libhardware_legacy" name="platform/hardware/libhardware_legacy" groups="pdk,bdk" />
   <project path="libnativehelper" name="platform/libnativehelper" groups="pdk,bdk" />