[dv] Update xcelium cover.ccf to only enable coverage for dut
[dv] Update xcelium cover.ccf to only enable coverage for dut

No need to collect code coverage at DV files
Signed-off-by: Weicai Yang <4fa8c7762ee4da95e3dee7dae2c3263ea16637f9@google.com>

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