doc(kmac): Update kmac_entropy test plan desc
doc(kmac): Update kmac_entropy test plan desc

This commit updates `chip_sw_kmac_entropy` test plan descrition. It was
outdated (wait_timer, operation mode etc)

Signed-off-by: Eunchan Kim <cb7bc7ceb22698f298c67faa994fd9ddf3cab298@opentitan.org>

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