[top] Fix typo in comment in top_earlgrey.hjson
[top] Fix typo in comment in top_earlgrey.hjson

This is "software clock gate", not "software config". The naming in
the actual code is sw_cg.

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

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