[otbn, dv] Fixes failures in otbn_imem_err when secure wipe is enabled
[otbn, dv] Fixes failures in otbn_imem_err when secure wipe is enabled

When secure wipe is enabled, wiping takes extra 98 cycles and if an imem
error is injected in this period, it will be ignored.
This commit increases the delay fron 3 ro 100 cycles to allow for secure
wiping to complete and then check for idle status.

Signed-off-by: Prajwala Puttappa <d42da9c1e7c0c7ddf8c0244ff16e57febc9395a0@lowrisc.org>

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