[util] Fix lint in dvsim.py
[util] Fix lint in dvsim.py

Python (and flake8 in particular) doesn't like tabulation of
dictionaries. This was added in commit 2de350a (in PR #2994), but
apparently our CI didn't run for that commit so we didn't notice the
breakage :-(

Signed-off-by: Rupert Swarbrick <290093e2ad2515ed2f14d749293c8cf8e02ca274@lowrisc.org>

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