bfd: bfin: drop needless symbol flag handling imported from FRV

The Blackfin bfd merged some FRV code recently, and then removed pieces
that didn't make sense.  In the FRV code, it outputs a "_gp" symbol in
its BFD whereas in the Blackfin code, we don't.  So while on the FRV
side it fiddles with the "flags" variable (sometimes using it for section
flags and sometimes using it for symbol flags), we don't need any of
that.  This lead to BZ 12177 where the Blackfin code is a bit confusing.
So to fix things up, remove more stuff we don't need.  Shouldn't change
the behavior at all.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>