opcodes: blackfin: fix decoding of 32bit addresses on 64bit systems

opcodes: blackfin: fix decoding of 32bit addresses on 64bit systems

The Blackfin ISA is very exact with regards to address truncation when
under/over flowing its 32bit range.  On a 32bit system, things work the
same and so addresses are decoded properly.  On a 64bit system though,
the decoded addresses may include the bits that are supposed to have
been truncated.  So force a 32bit truncation after the address has been
calculated.

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