ccd doc: link cr50 doc in main ccd doc
ccd doc: link cr50 doc in main ccd doc

BUG=none
BRANCH=none
TEST=verify link works

Change-Id: I774a0dc1c0965f3655c46b09ff9bdd3e12f21200
Signed-off-by: Mary Ruthven <81380f3403fed74252e92df3ed012a1819ec6296@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1599680
Commit-Ready: ChromeOS CL Exonerator Bot <fa429e5907f00867f797423aea74327bb02c91b6@appspot.gserviceaccount.com>
Reviewed-by: Kevin Shelton <7507f71ebb4f01db734916a11086d9489d89295e@chromium.org>
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