cr50: fix DEBUG_DRIVE comment
cr50: fix DEBUG_DRIVE comment

This is the DEBUG_DRIVE register, not the DEBUG_BLOCK_OUTPUT. Copy/paste
error?

BRANCH=none
BUG=none
TEST=none

Change-Id: Ic915b8675559d6f43d153f3a309becc621416dbe
Signed-off-by: Brian Norris <67059238af8e1945c40edb274ce1d51ba595dbf3@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/924698
Reviewed-by: Mary Ruthven <81380f3403fed74252e92df3ed012a1819ec6296@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec