README: update coveralls badge
README: update coveralls badge

We've moved our Coveralls repository to reflect the move of the Github
organisation from 01org to tpm2-software.

Signed-off-by: Joshua Lock <9750fc34162235efa862f2505c1a01f735e97af7@intel.com>

martinezjavier/tpm2-tools,01org/tpm2.0-tools,martinezjavier/tpm2-tools,martinezjavier/tpm2-tools,martinezjavier/tpm2-tools,01org/tpm2.0-tools,01org/tpm2.0-tools