Remove OpenHW/SiLabs copyright headers from unmodified Coremark files
This PR is the first step to resolve #1623 (closed).
It updates all of the Coremark license headers in core-v-verif/<core>/tests/programs/custom/coremark
to remove the OpenHW/SiLabs copyright from unmodified files.
@christian-herber-nxp
, if/when you sign off on this I will make the same changes to the cv32e20
branch.