cleanup setup_board for host board builds

Remove option of passing install plan filename used for reverse
dependency calculation for host board setups.

BUG=b:75396373
TEST=local builds

Change-Id: I205fe59b0f24b5c27dcaddf201f1791b7d11ef7a
Reviewed-on: https://chromium-review.googlesource.com/1055656
Commit-Ready: Gregory Meinke <gmeinke@chromium.org>
Tested-by: Gregory Meinke <gmeinke@chromium.org>
Reviewed-by: C Shapiro <shapiroc@google.com>
diff --git a/setup_board b/setup_board
index 2bbf1e2..b410c87 100755
--- a/setup_board
+++ b/setup_board
@@ -106,10 +106,10 @@
   || [[ -n "${FLAGS_brick}" ]]; then
   UPDATE_ARGS+=" --skip_toolchain_update"
 fi
-SAVE_INSTALL_PLAN_ARGS=""
 if [[ ! -z "${FLAGS_save_install_plan}" ]]; then
-  SAVE_INSTALL_PLAN_ARGS=" --save_install_plan=${FLAGS_save_install_plan}"
-  UPDATE_ARGS+="${SAVE_INSTALL_PLAN_ARGS}"
+  # If we are trying to calculate reverse dependencies pass the install
+  # plan filename to update_chroot.
+  UPDATE_ARGS+=" --save_install_plan=${FLAGS_save_install_plan}"
 fi
 
 if [ "${FLAGS_skip_chroot_upgrade}" -eq "${FLAGS_FALSE}" ] ; then