XCVR2450 tranceive hackish fix. Re-write the atr mask, io, and oe registers in the...

XCVR2450 tranceive hackish fix. Re-write the atr mask, io, and oe registers in the set_gpio().
usrp basic overwrites the registers on init and can be harmful to an app that uses both RX and TX.
set_gpio will be called when the frequency is set so tuning after initialization is required.
Also, the custom xcvr set register methods were replaced will calls to common_*

git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@10853 221aa14e-8319-0410-a670-987f0aec2ac5