Blackfin: change the BUG opcode to an unused 16-bit opcode

The current BUG opcode includes the bit that flags the insn as a 32bit
opcode, but it wasn't declaring it as 32bits.  So pick an unused 16bit.

URL: http://blackfin.uclinux.org/gf/tracker/5973


Signed-off-by: Robin Getz <robin.getz@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>