pfalcon-tf-m-code-coverage: Add LCOV_FLAGS param, default to --quiet

The idea is to remove noise from productions jobs, but still be able to
remove --quiet to debug codecov processing when needed.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: Ie1417c136e3ffceec73c191388a8230752fd0fac
1 file changed