Remove redundant files already tracked by tools/build/mk/OptionalObsoleteFiles.inc.

These files are installed, likely after r288230. In
tools/build/mk/OptionalObsoleteFiles.inc they are bound
to the MK_BINUTILS option rather than unconditionally
deleted here.

Reported by: Kurt Lidl <lidl@pix.net>
MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division