drop gdb mask for Blackfin targets

Now that gdb supports Blackfin targets, no need to mask it.

Signed-off-by: Jie Zhang <jie.zhang@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@168943 138bc75d-0d04-0410-961f-82ee72b054a4