[edn/doc] Update rw0c register description
[edn/doc] Update rw0c register description

Fix a small typo in regwen. The RW0C should be write value zero to set
the regwen.

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

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