mb/google/nissa: Create sundance variant

Create the sundance variant of nissa reference board by copying the
template files to a new directory named for the variant.

Due to new_variant.py limitation that repo can no longer be used in
inside, created this CL manually following google suggestion.

BUG=b:328505938
TEST=util/abuild/abuild -p none -t google/brya -x -a
make sure the build includes GOOGLE_SUNDANCE

Change-Id: Ia8ba318f18d2cac69898687311631778e61bf2ea
Signed-off-by: Leo Chou <leo.chou@lcfc.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/81347
Reviewed-by: Derek Huang <derekhuang@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <ericllai@google.com>
Reviewed-by: Shou-Chieh Hsu <shouchieh@google.com>
diff --git a/src/mainboard/google/brya/variants/sundance/overridetree.cb b/src/mainboard/google/brya/variants/sundance/overridetree.cb
new file mode 100644
index 0000000..4f2c04a
--- /dev/null
+++ b/src/mainboard/google/brya/variants/sundance/overridetree.cb
@@ -0,0 +1,6 @@
+chip soc/intel/alderlake
+
+        device domain 0 on
+        end
+
+end