[prim] IFDEF_CODE waiver in sparsefsm flop

unused_err_o is assigned in ifdef and else together.

Signed-off-by: Eunchan Kim <eunchan@opentitan.org>

hw/lint/tools/ascentlint/common.waiver

diff --git a/hw/lint/tools/ascentlint/common.waiver b/hw/lint/tools/ascentlint/common.waiver
index d150257..ec10ba2 100644
--- a/hw/lint/tools/ascentlint/common.waiver
+++ b/hw/lint/tools/ascentlint/common.waiver
@@ -10,3 +10,4 @@
 waive -rules {HIER_NET_NOT_READ HIER_BRANCH_NOT_READ} -regexp {gen_.*\.unused_.*}
 waive -rules {ONE_BRANCH} -regexp {unique case statement has only one branch}
 
+waive -rules {IFDEF_CODE} -regexp {unused_err_o} -location {prim_sparse_fsm_flop.sv}