[conn] Fix conn compile error
[conn] Fix conn compile error

This PR fixes the conn compile error because the `prim_sparse_fsm` has
too many loops inside `INC_ASSERT`.
Because conn test only compile design and does not need any assertions
or assumptions, I used `+define+SYNTHESIS` instead of `+define+FPV_ON`.

Signed-off-by: Cindy Chen <399ad771a111eac8923348b1e2af093034e5d4f1@opentitan.org>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan