ec: Document how to get coverage report for board
ec: Document how to get coverage report for board

Document the instructions on how to get test coverage for one legacy EC
board using eldrid as the sample.

BRANCH=None
BUG=None
TEST=Ran commands (Eldrid is 34%)

Signed-off-by: Jeremy Bettis <4df7b5147fee087dca33c181f288ee7dbf56e022@google.com>
Change-Id: Id62e3056c58e4c0e7e0008c8b8c3cc78f30e5b39
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3883767
Auto-Submit: Jeremy Bettis <4df7b5147fee087dca33c181f288ee7dbf56e022@chromium.org>
Reviewed-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>
Tested-by: Jeremy Bettis <4df7b5147fee087dca33c181f288ee7dbf56e022@chromium.org>
Commit-Queue: Jeremy Bettis <4df7b5147fee087dca33c181f288ee7dbf56e022@chromium.org>

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