Remove unused variables in fbsd-tdep.c files

i386-fbsd-tdep.c and amd64-fbsd-tdep.c failed to build on my x86-64
Fedora 34 machine, using the system gcc, after a recent patch.  These
two files now have unused variables, which provokes a warning in this
configuration.

I'm checking in this patch to remove the unused variables.
2 files changed