ccd doc: add more to information about using ccd
ccd doc: add more to information about using ccd

BUG=none
BRANCH=none
TEST=none

Change-Id: I5776c16032863a2a0f8d5c82f148c80822379dec
Signed-off-by: Mary Ruthven <81380f3403fed74252e92df3ed012a1819ec6296@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1599681
Commit-Ready: ChromeOS CL Exonerator Bot <fa429e5907f00867f797423aea74327bb02c91b6@appspot.gserviceaccount.com>
Reviewed-by: Aseda Aboagye <12c9b286316a940fd31c24070da5ab64cdd4d0e7@chromium.org>

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