Blackfin is a painful platform to work with, no test machines are available
and the range of multimedia applications is dubious. Thus it only represents
a maintenance burden.
Refactoring mmx2/mmxext YASM code with cpuflags will force renames.
So switching to a consistent naming scheme beforehand is sensible.
The name "mmxext" is more official and widespread and also the name
of the CPU flag, as reported e.g. by the Linux kernel.
