drivers: cc2520: Correct configuration options

At the moment CC2520 configuration options are selected inside "TI
CC2520 Driver RAW channe" submenu like:

           [*] TI CC2520 Driver support  ----

           [ ] TI CC2520 Driver RAW channel  --->

Make RAW channel depends on TI CC2520.

Change-Id: I92879b7f4391f1842c012b6c03c78956e90b9441
Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>