Remove the last vestiges of FDC_DEBUG & FD_DEBUG
FDC_DEBUG is not referenced in any c or header files but traces of it
still remain in other files.

PR: 105608
Reported by: Eugene Grosbein <ports AT grosbein DOT net>
Reviewed by: imp
Approved by: bcr (mentor)
MFC after: 7 days
Differential Revision: https://reviews.freebsd.org/D10303