sysutils/uefi-edk2-bhyve-csm: Mark port deprecated

This port requires an old version of edk2 from 2014, and
needs gcc 4.8 to build. Due to that and the fact that few
users should need BIOS compatibility these days, mark
it deprecated with an expiration date of April 1st, 2024.

Differential Revision: https://reviews.freebsd.org/D39028
Reviewed-by: manu
Approved-by: manu