radioDevice: better encapsulation in base class

It's not good style to have the derived classes initialize members
inherited from the base class using "this->foo = bar".  Rather, let's
make the base class have a constructor, and call that constructor to
initialize the members of the base class.

While doing this
* rename 'offset' to 'lo_offset' to avoid confusion with timestamp offset
* move 'InterfaceType' into the base class
* move 'chans' into the base class
* move 'rx_sps' into the base class
* mark base class members as 'protected'

Change-Id: Ib885675a7612a392aa7f75fca81269ddcff2f6ab
6 files changed