fix PR 6724 - convert m68k options to defflag's.  this means that
M680[12346] are now available from opt_m68k_arch.h.  FPSP meantioned
in the PR has already been fixed, and i could not find any more.

i built these kernels to ensure i did not break their builds:

amiga: GENERIC DRACO
atari: HADES FALCON MILAN-PCIIDE
mac68k: GENERIC
sun2: GENERIC
sun3: GENERIC GENERIC3X
cesfic: attempted GENERIC, does not build due to lack of machine/bus.h
hp300: GENERIC
luna68k: GENERIC
mvme68k: GENERIC
news68k: GENERIC
next68k: GENERIC
x68k: GENERIC

(mrg)