[committed] Fix length computation bug in bfin port

[committed] Fix length computation bug in bfin port

The tester seemed to occasionally ping-pong a compilation failure on the
builtin-bitops-1.c test.  I long suspected it was something like length
computations.

I finally got a few minutes to dig into it, and sure enough the blackfin
port was claiming the "ones" operation was 2 bytes when it is in fact 4 bytes.

This fixes the compilation failure for the builtin-bitops-1.c test.   Sadly,
it doesn't fix any of the other failures on the bfin port.

Committed to the trunk.

gcc/
	* config/bfin/bfin.md (ones): Fix length computation.