Removed format from usrp dual/simple sink. USRP sink does not have a

Removed format from usrp dual/simple sink. USRP sink does not have a
format option. Gave usrp dual/simple source a unified format option with
the only 2 choices possible:  (16, 0) and (8, 8). When and if future
options are available, these blocks will be modified as such. Until
then, these blocks reflect the capabilities in the current trunk.

git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@10787 221aa14e-8319-0410-a670-987f0aec2ac5